21. Although everything seems to have been taken into consideration, ____ accident can
happen when the astronauts walk in _____ space．
A．不填；the B．an；不填 C．the；the D．an；the
22. His wife is constantly finding ____with him,which makes him very angry.
A. errors B. shortcomings C. fault D. flaw
23. The water___cool when I jumped into the pool for morning exercise。
A．was felt B. felt C. is felt D.feels
