C语言挑选幸运观众，要求可录入幸运观众的名字，编号，电话，同时将基本信息保存在file05 txt中，满足可删除观众信息的功能，从已录入信息的观众随机挑选3个观众，并显示其信息，最后可以将3名幸运观众的信息保存在另一个文件中，最后可以满足退出系统的功能。同时该程序满足方便易懂，便利性强，请做出其程序

好的，以下是满足你要求的C语言程序：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>

#define MAX_NAME_LEN 20
#define MAX_NUM_LEN 10
#define MAX_PHONE_LEN 20
#define MAX_RECORDS 100

typedef struct {
    char name[MAX_NAME_LEN];
    char num[MAX_NUM_LEN];
    char phone[MAX_PHONE_LEN];
} Audience;

void save_to_file(Audience records[], int count) {
    FILE *fp = fopen("file05.txt", "w");
    if (fp == NULL) {
        printf("Failed to open file!\n");
        return;
    }
    for (int i = 0; i < count; i++) {
        fprintf(fp, "%s %s %s\n", records[i].name, records[i].num, records[i].phone);
    }
    fclose(fp);
}

int load_from_file(Audience records[]) {
    FILE *fp = fopen("file05.txt", "r");
    if (fp == NULL) {
        printf("Failed to open file!\n");
        return 0;
    }
    int count = 0;
    while (fscanf(fp, "%s %s %s", records[count].name, records[count].num, records[count].phone) != EOF) {
        count++;
    }
    fclose(fp);
    return count;
}

void print_record(Audience record) {
    printf("Name: %s\n", record.name);
    printf("Number: %s\n", record.num);
    printf("Phone: %s\n", record.phone);
}

void print_records(Audience records[], int count) {
    for (int i = 0; i < count; i++) {
        printf("Record %d:\n", i+1);
        print_record(records[i]);
        printf("\n");
    }
}

void delete_record(Audience records[], int count, char num[]) {
    for (int i = 0; i < count; i++) {
        if (strcmp(records[i].num, num) == 0) {
            for (int j = i; j < count-1; j++) {
                records[j] = records[j+1];
            }
            count--;
            printf("Record %s deleted.\n", num);
            break;
        }
    }
    save_to_file(records, count);
}

void select_lucky_audience(Audience records[], int count) {
    if (count < 3) {
        printf("Number of audiences is less than 3. Cannot select lucky audiences.\n");
        return;
    }
    srand(time(NULL));
    int selected[3];
    for (int i = 0; i < 3; i++) {
        int index;
        do {
            index = rand() % count;
        } while (selected[0] == index || selected[1] == index);
        selected[i] = index;
        printf("Lucky audience %d:\n", i+1);
        print_record(records[index]);
        printf("\n");
    }
    FILE *fp = fopen("lucky_audiences.txt", "w");
    if (fp == NULL) {
        printf("Failed to open file!\n");
        return;
    }
    for (int i = 0; i < 3; i++) {
        fprintf(fp, "%s %s %s\n", records[selected[i]].name, records[selected[i]].num, records[selected[i]].phone);
    }
    fclose(fp);
    printf("Lucky audiences saved to file.\n");
}

int main() {
    Audience records[MAX_RECORDS];
    int count = load_from_file(records);
    printf("Audience Management System\n");
    printf("-------------------------\n");
    printf("1. Add audience record\n");
    printf("2. Delete audience record\n");
    printf("3. Display audience records\n");
    printf("4. Select lucky audience\n");
    printf("5. Exit\n");
    int option;
    do {
        printf("Please enter your option (1-5): ");
        scanf("%d", &option);
        switch (option) {
            case 1:
                if (count >= MAX_RECORDS) {
                    printf("Maximum number of records reached.\n");
                    break;
                }
                printf("Please enter the name, number and phone of the audience: ");
                scanf("%s %s %s", records[count].name, records[count].num, records[count].phone);
                save_to_file(records, ++count);
                printf("Record added.\n");
                break;
            case 2:
                printf("Please enter the number of the audience to be deleted: ");
                char num[MAX_NUM_LEN];
                scanf("%s", num);
                delete_record(records, count, num);
                count = load_from_file(records);
                break;
            case 3:
                print_records(records, count);
                break;
            case 4:
                select_lucky_audience(records, count);
                break;
            case 5:
                printf("Exiting...\n");
                break;
            default:
                printf("Invalid option.\n");
                break;
        }
    } while (option != 5);
    return 0;
}

以上就是实现你要求的C语言程序，程序中使用了结构体来存储幸运观众的基本信息，并将信息保存在文件中。程序提供了添加、删除、显示观众记录和选择幸运观众的功能，用户可以根据自己的需求完成各种操作。同时，程序也对用户输入进行了有效性检查，确保了程序的稳定性。