Which statement is true about the elements fluorine, chlorine, and oxygen?
a. they are all halogens
b. they react easily with metals
c. they are similar to noble gases
d. they are all nonmetals

Lets start over and go through the options from the starting.
Option A. they are all halogens.
oxygen is not a fluorine is halogen, chlorine is halogen but oxygen does not belong to halogen. Oxygen belongs to chalcogen group. 
So it's not option A.

Option B. they react easily with metals.
These metal are considered the most reactive metals in the period table. 
So we can say that this can be true.

Option C. they are similar to noble gases.
We know that these element are not similar to noble gases. These elements are not in the gaseous state when formed.
So it's not option C.

Option D. they are all non-metals.
We all know that these elements are metal. So we can take it out immediately.
So it can't be even D.

So, our correct answer will be B.

Hope this helped.. :)

The answer is b. increased blood flow reduces nerve sensitivity