Since Tom_____ downloaded a virus into his computer, he can not open the file now.

It was raining hard. Little Tom felt cold, so he stood______to his mother.

After four years’ research, we now have a ______ better understanding of the disease.

At first,he doubted my honesty but at last he　　　　.

Although China has developed its economy greatly, its per capital GDP is still         one-tenth of the United States.