请帮忙看看这几个题该怎么做？

一个亲戚的孩子要去新加坡。这之前要有个考试，这是去年的考试题，我看着很难，请高手指教一下，谢谢~~
1.Van Gogh's Sunflowers___39.9 million dollars, three times the previous record.
A. once sold for B. for sale once C.selling for once D.for conce sold

2.It is gravity___objects toward the earth.
A.pulling B. that pulls C.to pull D.what pulls

3.Most accidents in the home can be prevented by ___ elimination of hazards.
A. that B.that the C.there is a D.the

4.People ususlly get a sufficient amount of the calcium their bodise___ from the food they consume.
A. need B.needs C.needing D.to need

5.A partenership is an association of two or more individuals who ____ together to develope a business.
A. worked B.they work C.work D.working
请问第1题为什么选A啊，我选的是D！！

1.Van Gogh's Sunflowers___39.9 million dollars, three times the previous record.
A. once sold for B. for sale once C.selling for once D.for conce sold

A 此处sold为不及物动词，“出售”之意。全句大意是：梵高的《向日葵》曾以三千九百九十万的价格出售，这是从前的记录的三倍。

2.It is gravity___objects toward the earth.
A.pulling B. that pulls C.to pull D.what pulls

B.It is ... that...是强调句型，被强调的部分放在that的前面。全句大意是：就是地球引力将物体拉向了地球。

3.Most accidents in the home can be prevented by ___ elimination of hazards.
A. that B.that the C.there is a D.the

D. 这个是显而易见的。

4.People usually get a sufficient amount of the calcium their bodies___ from the food they consume.
A. need B.needs C.needing D.to need

A.their bodies need是定语从句，修饰先行词calcium。从句主语是bodies为复数，所以用need。全句大意是：人们通常是从消耗的食物中获取他们身体所需的足够的钙的。

5.A partnership is an association of two or more individuals who ____ together to develop a business.
A. worked B.they work C.work D.working