完成句子 (共5小题；每小题2分，满分10分)
小题1:Walking does need a bit of practice ________ ________ ________ _________ _________(既然重力改变了).
小题2: He did not look forward to __________ _________ _________(欠债) because his restaurant was no longer popular.
小题3:At that time people would starve if food _________ __________ __________ __________(难以找到), especially during the cold winter months.
小题4:So ________ ________ _______ _______(是否生命能继续延续) on the earth for millions of years to come will depend on whether this problem can be solved.
小题5:You must come ________ _______ ______ (任何时候你想来) and have ________ _______ ________ (任何你喜欢吃的东西).