根据汉语意思，完成句子

小题1:正是他经常帮助我。

It is __________   __________ often __________ me.

小题2:昨晚，杰克宁愿呆在家里也不愿意出去散步。

Jack __________  __________ stay at home rather than _________ out for a walk.

小题3:那是他第一次去长城游览。

It was the first time that he __________   ____________ the Great Wall.

小题4:正当她要穿过马路时，突然听到有人叫她的名字。

She was __________   ___________ cross the street __________ she heard her name ___________ by someone.

小题5:他们下定决心去哪里度假了吗？

Have they __________  __________ their __________ where to spend their holiday?

冷却肉应放入冰箱的冷藏室中保存，使肉的周围保持较高的湿度和较低的温度，以防止( )对肉表面的变色作用，使肉保持鲜红的色泽。

A．空气中的二氧化碳

B．水分

C．空气

D．氧气