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Concept:The verb "await" means "wait for" and should not be followed by the preposition "for".
Explanation:The error is in part (b) of the sentence: "awaiting for".
The verb "await" already includes the meaning of "wait for".
Adding "for" after "await" is redundant and grammatically incorrect.
For example: "She is awaiting her results" is correct, not "awaiting for her results".
However, the verb "wait" can be followed by "for": "wait for the bus".
In the given sentence, "awaiting" should be used alone without "for".
The corrected sentence is: "The students were awaiting the arrival of the chief guest."
Thus, the underlined part (b) contains an error.
Answer:B