Adisadvantage of using a sentence outline instead of a topic outline is that a sentence outline is often
a. underdeveloped.
b. factually grounded.
c. rigid.
d. time-consuming

A disadvantage of using a sentence outline instead of a topic outline is that a sentence outline is often D. TIME-CONSUMING.

Topic outline - lists words or phrases related to the topic.
Sentence outline - lists complete sentences related to the topic.

Sentence outline arranges your sentences:
1) hierarchically (with its main and sub-points)
2) in the sequence you want
3) and shows what you will talk about
4) and shows exactly what you will say about each mini-topic.

Each sentence in the outline will serve as mini-thesis statement of the mini-topic. It contains the complete and specific idea that a thesis paper's section will cover as part of the overall thesis.