The proper way to write a large number in a sentence is: ten billion 10 billion 10,000,000,000 tens of billions the first option right?

The first two options are correct; Ten billion & 10 billion.

Explanation:

When we are writing we want it be as comprehensible as possible. Adding information that is hard to read can be distracting and the audience can lose interest.  For example take a look at the three sentences below:

Maria thinks that the world population is ten billion.

Maria thinks that the world population is 10 billion.

Maria thinks that the world population is 10,000,000,000.

The first two sentences are easily readable, but in the third sentence the reader starts counting zeroes, and therefore is distracted from the main subject and he may even decide to not pursue it further.

Therefore the first two are best options when writing a large number in a sentence.

the answer would be A.the author's use of dialogue and action to reveal a character