3 sentences TOEFL

[Idiot]

Hi all
Can you explain for me ???
1. Due to the refraction of light rays, this is impossible for the naked yey to determine the exact location of a star close to the horizon.

You will think B is a correct answer. OK, you are right. But I wonder why we can't use "closing" insted of "close". Now the sentece is:
Due to the refraction of light rays, this is impossible for the naked yey to determine the exact location of a star closing to the horizon.

It's OK ? Give me your explaination

2. Xanthines have both good and bad effects on the body, and these effects are generally determined on the size and regularity of dosage.

C is correct answer, but I don't know what is this here.

3. The Millicent Rogers Museum houses five thousands pieces of Hispanic and American Indian jewelry, textiles, and other objects documenting the vibrancy of these two cultures.

You will find out A is correct answer, five thousands-> five thousand. But I wonder about "documenting". I think "document" is correct. Please explain detail for me.

[uhcl]

Hi Idiot,

1. "close to" means "near". It's not a verb.
Ex: I want to sit close to you .
2. I can't find any mistake here.
3. Here it means "... objects which document the vibrancy...". When we reduce this structure we have "documenting".

HTH!