I forgot the time. I missed the play.(complex sentence)

I studied hard. I passed the examination.(complex sentence)

I'm a happy man now. I've solved my problem.(complex sentence)

The heavy rain started suddenly. We stopped planting our trees.(compound sentence)

Frank wanted to go swimming. Mary decided to go shopping.(compound sentence)

Jane works at the Family Planning Clinic. Her husband Smith does research work for the same unit.(compound sentence)

Mary had to give upsewing. Her arthritis had become very painful.(compound sentence)

He is reading and at the same time he is writing as well.(simple sentence)

The factory chimney smoked the air and the factory chimney polluted the air as well.(simple sentence)

I checked my paper again. I handed it to my professor.(complex sentence)