4. Europe North
Americ
a
Explanation Incorrect
Oestrus Estrus 18-24 hr
period of
sexual
receptivity
Oestrous
Oestrou
s cycle
Estrous
cycle
21 day sexual
cycle
Estrus cycle
or oestrus
cycle
Estrus is a noun.
The cow is displaying estrus(heat)
Estrous is an adjective.
Length of estrous cycle in cow is 21days