The correct options are
A →a = →−b
C →c = →−d
Negative of a vector →u is a vector having the same magnitude but the opposite direction.
Here
∣∣→a∣∣=∣∣∣→b∣∣∣
But →a is in opposite direction of →b
So →a=→−b
Similarly
∣∣→c∣∣=∣∣∣→d∣∣∣
So →c=→−d
→a and →c are not in opposite directions. So →a≠→−c
Same is the case with →b and →d