Read the sentence: the very elusive falcon flies too quickly to be easily captured.

which adverb modifies an adverb?

a. too
b. quickly
c. very
d. easily

A) too.

Explanation: an adverb is a word or phrase that modifies or qualifies an adjective, verb, or other adverb or a word group, expressing a relation of place, time, circumstance, manner, cause, degree, etc. In the given sentence we can see two adverbs: "quickly" that modifies the verb "flies" indicating manner, and the adverb "too" that modifies the adverb "quickly" indicating degree.

the present continuous is a verb tense which is mainly used to indicates that an action is in progress at the moment of speaking.  

it is formed using: person + verb to be (am/is/are) +verb + - ing form  

example: i am studying at this moment .

in addition, the present continuous is also used in order to express things that will or will not happen in the near future.

example: i am having dinner with some friends tonight.

the speaker sometimes   uses it   to express that an action is repeated and it causes irritation on the part of the speaker

example: my sister is constantly complaining about everything.