Answer:
D. A DOW is a truck with scientific equipment mounted on the back of it.
Step-by-step explanation:
Now, in order to answer correctly, we need to take a look at the sentence before and the sentence after this blank.
The sentence before introduces us to this new tool, its name and abbreviation.
The sentence after gives us short insight on the look of the truck.
Since this truck isn't mentioned anywhere before in the text, we can safely presume that the best fitting logical connection between these two sentences is the one which explains that this new tool is actually a truck, which is the answer D.