A blank element is a descriptive word, phrase, or clause that is not essential to the meaning of a sentence. answers:
a. compound
b. modifying
c. nonrestrictive
d. restrictive
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A nonrestrictive element or a nonessential element

A word, phrase or a clause that is not essential to the meaning of a sentence is referred to as a nonessential element.

When this type of element is removed from a sentence,the sentence still makes sense since it is not essential.

For example;

In the sentence; The information, however, was inaccurate.

However is the non essential element since it interrupts the flow of the sentence, removing it the sentence would still make sense. that is;  

The information was inaccurate.

Explanation:

Have a lovely day <3

the maximum speed limit is 55 mph on a two-lane undivided highway and for vehicles towing trailers.