易错点1 名词的单复数形式的误判
【典例】 —What do you think the _____should do first?
—They should learn to take_____ as well as share rights in life.
A. grown-up; responsibility B. growns-up; responsibility
C. grown-ups; responsibilities D. growns-ups; responsibilities
错因分析：有些考生以为grown是复合名词的中心词，其复数形式应该在grown后面加-s；另一方面认为responsibility是不可数名词，没有复数形式，从而错选B。其实，grown-up没有中心名词，其复数形式应该在up后面加’s；同时根据语境可知，responsibility指义务，该单词作"义务，职责"讲时，可作可数名词或不可数名词，故正确答案选C。
拓展：复合名词的复数形式一般在中心名词后面加’s，如：looker-on → lookers-on, son-in-law → sons-in-law；但是当复合名词没有中心名词时，其复数形式是在最后的词后面加-s，如：grown-up → grown-ups; go-between → go-betweens。