Narwhals can be called whales of ice: in icy channels, ponds and ice-s

@skamal

Pl follow this example.

1. X ate water melon, his children looking at him —This is a simple sentence where x is the subject, and ate is the verb and the fruit, the object; What follows after the comma is a simple phrase, without a verb( looking’ is a present participle , not a verb) . We cannot use an ‘and’ in this case after the watermelon because and we can join only two equal things, be it two clauses or phrases or simply words. The word ‘and’ prevents the modifier phrase from being grammatically attached to the IC.
2. X ate watermelon as his children looked at him --- This is complex sentence, involving an independent clause (IC) and a dependent clause, both of which have their own verbs and hence they are called clauses. The word ‘as’ is a subordinate conjunction and now after having used a subordinate conjunction, we cannot use again another co-ordinate conjunction such as ‘and’.
3. When you follow an IC with and, then what must follow must also be an IC. Since ‘and’ is not underlined and since that will be part of any answer, then the only choice that will go with that structure is a clause that has a verb in the second arm ; only C has that structure.

I hope it is clear now why A violates sentence structure