21.A. should B. will
C. can D. must
22.A. concerned about B. interested in
C. happy with D. afraid of
23.A. lose heart B. get excited
C. gain confidence D. stay calm
24.A. faced B. brought
C. exposed D. connected
25.A. In reality B. In nature
C. On the contrary D. On one hand
26.A. in B. during
C. among D. on
27.A. unusually B. unlikely
C. ordinarily D. normally
28.A. in B. under
C. by D. about
29.A. dangerous B. risky
C. unsafe D. endangered
30.A. established B. blocked
C. offered D. destroyed
