Recent studies have discovered that fathers uniquely contribute to the development of their children, _____in low income families.

The boys are doing no harm; they are ___ playing．

A new study of HIV-infected people in Haiti indicates that starｔing treatment early could save many patients who might _______ die of AIDS.

. ---Do you get together with your old friends?---Yes, from time to time, but not ___ ___.

The meeting is beginning at 8 o’clock. _____, let’s make some preparations for it.