The plane is flying ________ the clouds.
A. above
B. on
C. on to
D. over
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The big tree our classroom is _____100 years old.
A. nearly
B. near
a picture ____ the wall （墙上的画）
人类核苷酸切除修复过程中,在损伤点5'端切割DNA单链的是
A.XPA
B.XPC
C.XPF
D.XPG
E.RPA
下列DNA损伤修复系统中,属于易错修复的是
A.错配修复
B.重组修复
C.光复活修复
D.碱基切除修复
E.核苷酸切除修复
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