The ratio of dry matter production to the assimilation of a particular nutrient element, usually expressed as grams per gram is called ( )

A relationship of two organisms living together (symbiosis) and one derives its nourishment at the expense of the other is called ( )

The number of individuals of a population the environment can support is ( )

汉译英：我去观光了5天。

A. I went sightseeing for five days.
B. I had a sightseeing tour for five days.
C. I went shopping for five days.
D. I went traveling for five days.

--May I help you？You seem to be having some problems.-- . thanks. I will manage

A. It's all right.
B. No problem
C. ok

--Which one of these do you want?--Either will be ok.

A. I'm sure
B. Go ahead.
C. I don't mind.

-The English Speech Contest has been cancelled.--Oh，no!

A. It's OK
B. what a pity！
C. It's pretty good.

--Have you paid? What's my share of the bill?-- . It doesn't take much money.

A. It's my share.
B. Don' worry about it.
C. It's none of your business.

--I'm going to Europe for a few weeks.-- .Have a good trip.

A. long time no see
B. Wish you succeed
C. It sounds so good.

--How is everything, Jonny?--

A. Very well, thank you.
B. Not too bad.
C. Sounds good