Question

Select the option that modifies the underlined phrase into a clause in the sentence given below:
Being late, she missed her flight. [Advanced]

• A. NO CHANGE
• B. Because she was late
• C. After she was late
• D. After being late

Answer 1

The correct option is B Because she was late

An adverb clause is a group of words containing a subject and a verb, and it functions as an adverb, by modifying an adjective, verb or an adverb. Adverb clauses generally begin with a subordinate conjunction (since, because, while, etc.)
Generally, while expanding an adverb phrase to a clause, the subject is added and the present participle (verb + ing) is changed into a verb. (If there is an auxiliary/helping verb required, it is added.)
The underlined words form a phrase, it has no subject. Hence the sentence needs to be changed and option A is incorrect.
Option B is correct because the subject "she" is added and the verb "was" replaces the present participle "being". Also, the adverb of cause "because" is added.
Option C is incorrect because the adverb "after" isn't relevant, it refers to time; the more relevant adverb here is that of cause.
Option D is incorrect because it is still a phrase, with the addition of an adverb.
Note: an adverb phrase may or may not contain an adverb, as long as it functions as one.