The police always takeadvantage of dogs’ ____ sense of smell to search for something.

If a healthy environment is gone, ________ everything that our life depends on.

Is your Uncle Tom a soldier—No, but he once _______ in the army for 4 years.

We haven’t seen each other for 20 years, but I recognized him _____ I saw him．Which of the following is wrong ?

She was so________that she wouldn’t give in until she received a full apology