Whereas a typical Master's thesis is approximately one

[BTGmoderatorDC]

Whereas a typical Master's thesis is approximately one hundred pages long, Ph.D theses is usually over two hundred pages.

A) Whereas a typical Master's thesis is approximately one hundred pages long, Ph.D theses is usually
B) A typical Master's thesis is approximately one hundred pages long, while a Ph.D thesis is generally
C) A typical Master's thesis is approximately one hundred pages long, so a Ph.D thesis is usually
D) While typical Master's theses is approximately one hundred pages long, Ph.D theses is generally
E) Whereas a typical Master's thesis is approximately one hundred pages long, a Ph.D thesis is

[deloitte247]

This is purely an academic affair. (chuckles) let's drive down to the options available to check which is the most correct.

In Option A - INCORRECT
We have an ugly situation on our hands. ''Master's thesis'' is in singular form while Ph.D thesis is in plural form. This is a case of inconsistent use of tenses.

In Option B CORRECT.
There's a consistent use of tenses here, if we see clearly the Thesis appears on both sides in the singular form.

In Option C - INCORRECT.
The statement formation does not flow well. The first lines of the sentences doesn't flow with the second. It appears like it's saying ''consequently wrong.

In Option D - INCORRECT
Here, a funny blunder has been committed. You can't use a plural noun ''theses'' and follow it up with a singular verb ''is''. It should be ''are''. It amounts to abuse of words.

In Option E - INCORRECT.
This statement is correct but it takes the form of the original sentences which is clearly not what we want. Just a change of the inconsistent ''thesis'' doesn't qualify the option E to become a right option overnight.