My mother some washing when the telephone rang．（ ）
A．doesB．didC．is doingD．was doing
How time flies！We should show love for our parents and make them ______how much they mean to us．（ ）
A．to knowB．knowingC．knewD．know
All the students _____ know cheating in the exam is not allowed．（ ）
A．needB．mayC．mustD．can
Two disabled men from Hebei Province （one is blind and the other has no arms） have spent over ten years____ trees together．（ ）
A．plantB．plantsC．plantingD．planted
We must protect plants because they are friends of____．（ ）
A．weB．usC．ourD．ours
Prime Minister Li Keqiang arrived in Shiyan____May 23nd，2016．（ ）
A．atB．onC．inD．from