问题
选择题
—Why are you standing there, Maggie?
—I can't see the blackboard clearly. Two tall boys are sitting _______ me. [ ]
A. behind
B. in front of
C. beside
答案
答案：B
搜题请搜索小程序“爱下问搜题”
—Why are you standing there, Maggie?
—I can't see the blackboard clearly. Two tall boys are sitting _______ me. [ ]
A. behind
B. in front of
C. beside
答案：B
2SO3已经达到平衡的密闭窗口中，充入少量由18O构成的氧气，片刻后，则18O存在于[ ]