The correct syntax for declaring a pointer to an integer is 'int *ptr;' where the asterisk (*) indicates it is a pointer variable.

sizeof(int) returns the size of integer in bytes as an integer value. On most modern systems, this is 4 bytes, and printf with %d will print this numeric value.

Both syntaxes are valid in C. Option A explicitly specifies both dimensions, while Option B lets the compiler calculate the first dimension based on initialization.

In C, an identifier cannot start with a digit. It must start with a letter (a-z, A-Z) or underscore (_). Option B violates this rule by starting with a digit.

In C, single quotes (') are used for single character constants (char type), while double quotes (") are used for string literals (array of characters ending with null terminator).

The 'break' statement is used to exit or terminate a loop or switch statement immediately. It transfers control to the statement following the loop or switch.

A 2D array in C is declared using the syntax: datatype arrayName[rows][columns]. So 'int arr[3][4];' creates a 2D array with 3 rows and 4 columns.

The array has 5 rows and 3 columns, so total elements = 5 × 3 = 15 elements. Each int typically occupies 4 bytes. Total memory = 15 × 4 = 60 bytes (assuming sizeof(int) = 4 bytes on most systems).

The do-while loop executes the body at least once before checking the condition. The syntax is: do { statements; } while(condition);. In contrast, while and for loops check the condition first.

Variables declared inside a block (enclosed in curly braces) have local or block scope. They are accessible only within that block and cease to exist once the block execution is complete.