Hi Chao and ChrisLuke

Thanks for the essay Chao and for the comments ChrisLuke!

The essay is nice and short at 269 words, and it's fairly easy to read, although the 20-word average is too high. I'd really try hard to write shorter sentences. ChrisLuke has identified three or four sentences which could be split into two -  there are more.

One sentence which puzzled me (and ChrisLuke) was this one

In addition, what effects would the food produced by modifying their genetic makeup have on human beings are still unknown.

It's got a word-order problem. Here's a possible rewrite:

In addition, what effects the food produced by modifying their genetic makeup would have on human beings are still unknown.

Or we could simplify and shorten it a little:

In addition, we still don't know the effects of genetically modified food on our health.

Thesis Sentence

Chao, I would definitely add a thesis sentence to your intro. Your intro is too short and the reader is puzzled about what you are going to do in the essay. You can read more about Thesis sentences here.

Watch for wordy sentences, as ChrisLuke suggests. Here's one which rambles on a little:

Also, more kinds of food have been offered in the market, which gives people more choices when they are deciding what will be served for dinner or lunch.

It's 28 words long, which is just too long. We could squeeze more ideas in if we eliminated unnecessary words:

Also, more kinds of food are available, so consumers have more choices. This could lead to healthier diets with more variety, and fresh foods all year round. 

Twenty-six words AND two extra ideas!

Conclusion

I would also write your conclusion as two or three sentences. One sentence has to do too much work. You can read more about conclusions here.

Break this 52-word monster up into several sentences in which you summarize both sides, give your opinion and look to the future.

Overall

Chao, you have a nice style in your writing. I hope you get some time to comment on some of the other essays here. Lots of new ones, so plenty to choose from! People really appreciate it! 

Thanks again to both of you!