公比为2的等比数列{an}的各项都是正数，且a3a11＝16，则a5＝________.
1
由a3a11＝16，得＝16，故a7＝4＝a5×22⇒a5＝1
根据首字母和汉语提示完成单词。
1. In the USA, when you get a present,you must open it i______.
2. In China, when someone gives you a present,you must w______ and open it later.
3. When you ______(接受) a present,you must use both hands.
4. You mustn't do any c______ on the first day of the Chinese New Year.
5. In China, people eat lots of d______ at Spring Festival.
对于大、中型湖泊与水库，当平均水深小于10m时，取样点在水面下0.5 m，但距湖、库底不应小于( ) m。
A．0.2
B．0.3
C．0.5
D．0.7
＝16，故a7＝4＝a5×22⇒a5＝1
＝16，故a7＝4＝a5×22⇒a5＝1