某吸热反应逆反应的活化能是20kJ/mol,正反应的活化能为:()
A.-20kJ/mol
B.小于20kJ/mol
C.大于20kJ/mol
D.无法确定
参考答案:C
甲海拔500米,乙海拔150 米,则二者的相对高度是( )
A.300米
B.650米
C.350米
D.200米
根据句意及首字母提示补全单词。
1. —How long has your father been a doctor?
—F_______ twenty years.
2. —What's your hobby?
—I like c_______ stamps very much .
3. If you know the answer, please r_______ your hand.
4. "Jim skates well" means he is a good s_______ .
5. Sam has been skating s_______he was six