He has been very interested in doing research on _______ since he was at high school.

A/ an ____ species is a population of an organism which is at risk of becoming extinct.

____ is a branch of Natural Science, and is the study of living organisms and how they interact with their environment.

My mother used to be a woman of great _______, but now she gets old and looks pale.

They had a ______ dinner last night and she accepted his proposal of marriage.

Choose the best answer to complete the following sentences.

People should be told about the things that threaten the safety of ____ so that they can avoid doing them.

Only a few of the many species at risk of extinction actually make it to the lists and obtain legal ____.

John cannot make a _______ to get married to Mary or stay single until he can afford a house and a car.