Answer:
D. In particular.
Explanation:
The use of the phrase "in particular" points to the specificity of the thing or person talked about. It is used to make particular reference to a thing or person.
In the given sentence, the blank will be filled by "in particular" because it shows the specific type of flowers that hummingbirds are attracted to. By pointing out that "tubular or trumpet shapes" are particularly liked by them, it specifies the type of flowers they like.
So, the sentence will be-
<em>"Hummingbirds are attracted to all flowers, </em><u><em>in particular</em></u><em>, those with tubular or trumpet shapes."</em>
Thus, the correct answer is option D.