The floor is dirty and it requires _________.
More and more people choose to shop in a supermarket as it offers a great _____ of goods.
It was really very dangerous. One more step, ______ the baby would have fallen into the well.
It is usually warm in my hometown in March, but it ________be rather cold sometimes.
No one had told Smith about __________ a lecture the following day.
If the food tastes nice, we will buy some; if ________, ________.