One way to ________ species under threat of extinction—whatever the cause—is to remove them to zoos or parks and feed them there.
31.The fact that smoking is harmful to health is____most smokers are quite aware of.
30.It was_________ back home after the experiment.
29.An example of them is fraud, a crime _______ money is stolen by cheating others.
28. Dr. Frank failed many times but he finally _____ to find a successful way to solve the problem.
27.---Where have you been? ---I got caught in traffic, otherwise I _______ here earlier.