若用小球表示原子，则分子模型可用于表示（ ）
F e
H 2
C O 2
N H 3
Now，people have more free time．Square Dancing is becoming___．（ ）
popular and popular
more popularer
popularer and popularer
more and more popular
The man over there ___ be our teacher．Our teacher is studying in France．（ ）
must
mustn't
can
can't
I like dumplings ___ my grandmother cooks．（ ）
that
who
where
when
The sea is large and full of water．It covers about ___of the planet．（ ）
three fourth
three fourths
third fourth
third fourths
My friend Henry was born ___June，1997．（ ）
in
on
at
for
可用于表示（ ）
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