Some TOEFL grammar ques: such few; resisting/resisted; periods of aviation

Dear,

I got these question in a Toefl grammar test:

1. Multinational companies have developed to the point where such few cars can be described as having been made entirely in one country.
2. Scientists believe that by altering the genetic composition of plants it is possible to develope specimens that are resisting to disease and have increased food value.
3. The early periods of aviation in the United States was marked by exhibition flights made by individual fliers or by teams of performers at country fairs.

The 1st sentence, the mistake is at "such few", but I dont know how to correct.

The 2nd sentence, they said the mistake is "resisting", that means "resisted" is correct. But I think those speciments themself resist to disease and have high food value, so, I must use "resisting" and "increased".

The 3rd sentence, the mistake is at "periods of aviation". I guessed the correction would be "period of aviation". But I can't explain why.

Please help me!

Thank you!

But could you explain more detail about the problems of the 2nd sentence.

I also have 2 more sentences to do:

4. Being the biggest expanse of brackish water in the world, the Baltic Sea is of special interesting to scientists.

5. The main advertising media include direct mail, radio, television, magazine, and newspaper.

6. While studying the chemistry of human body, Dr. Yalow won a Nobel Prize for the research she conducted on the role of hormones.

I don't know where the mistakes are in the 5th and 6th senctences. In the 4th sentence, I think both "is of" and "interesting" are incorrect. Am I right?

"of human body" might be the mistake in the 6th sentence, 'cos my dictionary has an example "the human body". But in that dictionary also has "human life" "human error", so is "the" neccessary before "human body"?

Averell wrote:

Thank you! But could you explain more detail about the problems of the 2nd sentence.