1.Helping others is a habit,__________you can learn even at an early age.
A.it
B.that
C.what
D.one
2.The country has already sent up three unmanned spacecraft,the most recent ______at the end of last March.
A.has been launched
B.having been launched
C.bing launched
D.to be launched
3.--I'm sorry I broke the vase
--Oh,_______.It wasn't very expensive.
A.you'd better not
B.I'm afraid not
C.as you wish
D.that's all right
4.Knowing office rules--whether _______or not--is critical,especially for young job seekers.
A.written
B.writing
C.being written
D.having been writte,
5.______to too much sunlight,as is generally considered,will add to the potential of catching skin cancer.
A.Being exposed
B.Exposed
C.Exposing
D.To expose