In the after-class activities,the students had plenty of______and gained aA.exercise,experienceB.practices,experienceC.practice,experienceD.exercise,experiencesIn the after-class activities,the students had plenty of______and gained a lot of practice________A.exercise,experienceB.practices,experienceC.practice,experienceD.exercise,experiences

B.practices,experience
plenty of后面加可数，这里用复数______and gained a有A 所以是单数。
问题补充：In the after-class activities, the students had plenty of______and gained a lot of practice________
A.exercise, experience
B.practices,experience
C.practice,experience
D.exercise,experiences
改题啦，那选项不用改。后面的单复都行。都解释通，不影响。
不过，都用复数好些，就是没得选

b 因为exercise在这个题中要用复数,
后面experience
当做经历讲,是可数名词,所以选择b
希望可以帮到你呵呵