anon1 wrote:
Narwhals can be called whales of ice: in icy channels, ponds and ice-shielded bays they seek sanctuary from killer whales, their chief predator, and their annual migrations following the seasonal rhythm of advancing and retreating ice.
Colon "
:" is usually used to give more information about preciding clause. Here, it explains why Narwhals can be called whales of ice.
More importantly, Let's keep in mind that "and" in red shows "parallelism".
(A) their annual migrations following
1) Now, after "and", we have a noun, "their annual migrations". Hence, We should find another noun parallel to it. We have two possibly but illogically parallel nouns. Let's make it more clear
1) "killer whales"
2) "sanctuary"
1) Narwhals seek sanctuary from killer whales and [Narwhals seek sanctuary from] their annual migrations...
2) Narwhals seek sanctuary from killer whales and [Narwhals seek] their annual migrations...
Both are illogical.
(B) their annual migrations which follow
(C) their annual migrations follow
1) Here, after "and", we have a clause: "their annual migrations follow...". Hence, this clause must be parallel to the preciding clause "...they seek sanctuary...". CLAUSE + AND + CLAUSE. Both clause exlain why "Narwhals can be called whales of ice".
(D) whose annual migrations following
1) After "and", we have "whose". Yet, we don't have another such structure in the sentence.
(E) whose annual migrations follow
1) the same issue as with (D)