After she had explained everything clearly, we started our work. A.Before we started our work, she had explained everything clearly. B.Before she started our work, we had explained everything clearly. C.Before we started our work, she explained everything clearly. D.Before we had started our work, she had explained everything clearly. 38.This is the first time I have had such a delicious meal. A.I had eaten such a delicious meal before. B.I hadn’t eaten such a delicious meal before. C.I have eaten such a delicious meal before. D.I haven't eaten such a delicious meal before. 39.You should water these flowers everyday to make them fresh. A.These flowers should be watered everyday to make them fresh. B.These flowers should watered everyday to make them fresh. C.These flowers should being watered everyday to make them fresh. D.These flowers should been watered everyday to make them fresh. 40.Although Singapore is a developed country, it is not polluted by industry. A.Despite being a developed country, Singapore is not polluted by industry. B.Despite a developed country, Singapore is not polluted by industry. C.Despite of being a developed country, Singapore is not polluted by industry. D.Despite of a developed country, Singapore is not polluted by industry.