有些射性元素要经历一系列的衰变才能稳定，关于X、Y、Z三个原子核的衰变方和如下：

X→ ${}_{82}^{206}$ Pb+8 ${}_2^4$ He+6 ${}_{-1}^0$ e    

Y→ ${}_{82}^{207}$ Pb+7 ${}_2^4$ He+4 ${}_{-1}^0$ e 

Z→ ${}_{82}^{208}$ Pb+6 ${}_2^4$ He+4 ${}_{-1}^0$ e

根据以上方程可以推断在X、Y和Z中，下列正确的是（   ）

用长2cm，宽1cm的长方形，拼成两种不同的长方形．把你拼出的长方形画在下面的方格纸上，并计算出它们的周长．

In China, primary school has more ____  (woman) teachers.
Chinese people all dress____  (they) in the best clothes when important festivals come.
The guide has collected the ____  (visit) ID cards since they arrived at this five-star hotel.
Her red dress makes her look much____ (pretty).
Cut the apple into____  (half). Then we can share them.
I am waiting for my turn____  (make) a wish at the table with my friends.
I look forward to____  (dress) up as Monkey King.
Does this pair of glasses____ (match) my jeans?
Some students don’t know how to have ____  (funny) at weekends.
The two children ____  (agree) about everything and always argued.