— Let's _____ table tennis after school.
— Good idea.
play
playing
to play
plays
Let's +动词原形。
— _________ your coat,it's cold outside.
— OK,Mum.
take off
put on
put off
take off 意为“脱下；飞机起飞”；put on 意为“穿上”；put off 意为“推迟”。根据题意可知，外面比较冷，需要穿上外套。故选B。