1. English is＿＿＿ useful language in ＿＿＿ world.
A an, the B a, the C the, / D /,the
2. What ＿＿＿ interesting book it is!
A a B an C the D /
3. He will be back in ＿＿＿ hour.
A / B the C a D an
4. He usually goes to school on ＿＿＿ foot.
A a B an C the D /
