Only after a baby seal is pushed into the sea by its mother _______to swim.
| A． how will it learn | B．will it learn how |
| C． it will learn how | D．and it learns how |
It is ten years since we ________ each other last time．
| A．see | B．have seen | C．saw | D．had seen |
More wild tigers have been seen in the forest around this area, ________ there used to be very few.
| A．when | B．where | C．what | D．which |
It is usually warm in my hometown in March, but it ________ be rather cold sometimes.
| A．must | B．can | C．should | D．would |
You can never be ________ when crossing the street．
| A．very careful | B．too careful |
| C．carefully enough | D．enough careful |
________, you need to give all you have and try your best．
| A．Being a winner | B．To be a winner |
| C．Be a winner | D．Having been a winner |