In which of the following exchanges is there a grammatic mistake?
A.
---Have they removed their furniture? ---They have done the desks, but that's all so far.
B.
---Does granny look after you every day? ---She can't do at weekends, because she has to go to her own house.
C.
---Can lions climb trees? ---No, but leopards can.
D.
---Did the lions seem hungry? ---No, but they did restless.