. To their great fear, they found ____ in the heaviest snowfall they had ever had.
| A．they were catching | B．themselves caught |
| C．they had caught | D．themselves catching |
Leave your key with a neighbor _______ you lock yourself out one day.
| A．ever since | B．even if | C．soon after | D．in case |
Small sailboats can easily turn over in the water ______ they are not managed carefully.
| A．though | B．before | C．until | D．if |
Most birds find it safe to sleep in the trees, but ________they have eggs or young chicks, they don’t use a nest.
| A．why | B．how | C．unless | D．where |
You will be successful in the interviewyou have confidence.
| A．before | B．once | C．until | D．though |
I won’t call you, ________ something unexpected happens.
| A．because | B．whether | C．unless | D．while |