2. Choose the correct alternative (past simple or past continuous). Lucky accidents

Is it true that Sir Isaac Newton understood gravity because an apple (1) fell / was falling on his head when he (2) lay / was lying under a tree in his garden? Probably not. However, many great and small discoveries are the result of lucky accidents...
One day in 1879 chemist Constantin Fahlberg (3) didn’t wash / wasn’t washing his hands before dinner. While he (4) ate / was eating he (5) noticed / was noticing that the bread (6) tasted / was tasting sweet. The sweetness was saccharin.
Alexander Fleming (7) became / was becoming interested in the control of bacteria while he (8) worked / was working as a doctor during the First World War. In 1928 he (9) tidied / was tidying his laboratory when he (10) saw / was seeing that one of the dirty dishes (11) didn’t have / wasn’t having any bacteria on it, but that something else (12) grew / was growing there. It was penicillin.
In 1930 dietician Ruth Wakeield (13) prepared / was preparing some cookies for guests when she (14) realised / was realising that she had no chocolate powder. She (15) decided / was deciding to use small pieces of ordinary chocolate instead. The chocolate pieces (16) didn’t melt / wasn’t melting, and the first chocolate chip cookies were a great success.
Dr Percy Spencer was a physicist in the 1940s who probably enjoyed chocolate chip cookies. He (17) walked / was walking past some equipment in the laboratory when he (18) felt / was feeling something strange in his pocket. It was his chocolate bar and it (19) melted / was melting. This accident (20) led / was leading to the invention of a new piece of cooking equipment – the microwave oven.​