Ⅰ.用适当的连词填空
1.(2015·浙江改编)If you swim in a river or lake,be sure to investigate is below the water surface.Often there are rocks or branches hidden in the water.
2.(2015·四川改编)The exhibition tells us we should do something to stop air pollution.
3.(2015·重庆一中一诊改编)To improve the quality of our products,we asked for suggestions had used the products.
