Which of the following are true about the PUSH instruction?

a$)$ It increments the stack pointer $($by $2$ or $4)$ and copies the operand in stack at the location pointed to by the stack pointer.

b$)$ It decrements the stack pointer $($by $2$ or $4)$ and copies the operand in stack at the location pointed to by the stack pointer.

c$)$ It increments the stack pointer by $1$ and copies the operand into the the location pointed to by the stack pointer.

d$)$ It copies the operand into the stack at the location pointed to by the pointer, and then decrements the stack pointer $($by $2$ or $4).$