Last night we went to Ann's party,____weenjoyed very much.[ ]

A. when    

B. that        

C. which      

D. where

抽油机井碰泵操作不仅可以排除泵阀轻微砂卡、蜡卡故障，还可以验证抽油杆是否下到位或是否断脱等。