1. What does a struct let you do that an array can't?
2. In a union, how many members can hold a valid value at one time?
3. What determines a union's total size?
4. Which function allocates memory AND initializes it to zero?
5. What happens if you forget to call free() on allocated memory?
6. Why should you check if malloc() returned NULL?
7. Which fopen() mode overwrites existing file content?
8. Why must you call fclose() after working with a file?
9. Which function reads a full line safely from a file?
10. What does realloc() do?