I would say D. because of how scrawny is a negative word.
An example:
Skinny, thin<span>, and slender</span><span>. </span><span>These three words all mean having less weight on one's body than what might be considered average. But the connotations differ since the suggested meanings of </span><span>skinny </span><span>and </span>thin <span>are often more negative than </span>slender<span>, with </span>skinny potentially the most negative of the three<span>.
It is the same for scrawny, thin, petite, and little. </span>
I would go for doing a burst of physical activities, as when you do these, endorphins are released, and you can focus better afterward.
The tense of the verb phrase "will invest" is D. future.