下列描述物质的变化中，不属于化学变化的是（   ）

-- Jack, I haven't seen your uncle for a long time.

-- He _____ Shanghai on business for two mouths.

. The main fact(or)s in human life are five: birth, food, sleep, love and death. (One could increase the number— add breathing for instance— but these five are the most obvious.) Let us ask ourselves ________ our lives.

读拼音，写汉字。

fǔ mō	ēn qínɡ	bào dá	yǒnɡ yuǎn	zhù shì
____	____	____	____	____

设随机变量的分布列为 $P\left(\xi =k\right)=\frac{c}{2^k}\left(k=1,2,3\right)$ ，其中 $c$ 为常数，则 $E\xi =$ ____.