sizeof(s) includes the null terminator '\0'. "hello" has 5 characters + 1 null terminator = 6 bytes. If s was a pointer, sizeof would give pointer size.

Modulus, multiplication, and division have equal precedence (left-to-right): (5 % 2) = 1, then (1 * 3) = 3, then (3 / 2) = 1 (integer division). Answer is 1, not 2. Correction: 1 is correct.

In a union, all members share the same memory location. The size of the union equals the size of the largest member. Only one member can hold a value at a time.

*p dereferences to a (10) and *q dereferences to b (20). Adding them: 10 + 20 = 30. Pointer arithmetic is used correctly here.

The correct syntax is 'int *p;' where int is the data type, * indicates pointer, and p is the pointer variable name.

The pre-increment operator ++x increments x first (from 5 to 6), then assigns the new value to y. So x = 6 and y = 6.

The free() function deallocates (releases) memory that was previously allocated using malloc(), calloc(), or realloc().

The correct syntax uses the 'struct' keyword followed by the structure name and then the member declarations enclosed in braces.

The do-while loop executes the body first and then checks the condition, ensuring at least one execution. while and for loops check the condition first.