Step 1: Interpret the poem.
The poem begins with the search in the external world ("I sought a soul in the sea"), where the poet finds only superficial objects like "coral" and "foam." This highlights the inadequacy of looking for deeper truths outside.
However, when the poet turns inward ("Into my heart's night"), moving along an uncertain, narrow path, he discovers illumination and vast possibilities ("The light, an infinite land of day").
Step 2: Match with the options.
- (A) "What lies outside is always deceptive" — too extreme; the poem does not condemn the outside entirely, it only emphasizes deeper truths within.
- (B) "Pursue the narrow path and avoid the broadways" — narrow path is mentioned, but the focus of the poem is not simply on rejecting broadways; it is about inner exploration.
- (C) "External search is futile; explore the inner space for answers" — this perfectly aligns with the poem’s essence, contrasting outside search with inner discovery.
- (D) "Heart’s pathways are broad and clear" — incorrect, the poem speaks of a "narrow way," not broad pathways.
- (E) "Light offers sight and insight" — partially true, but does not capture the central contrast between external and internal search.
Step 3: Conclude.
The poem emphasizes that the real truth and enlightenment come from within, not from external searches. Hence, the best option is (C).
\[
\boxed{\text{Correct Answer: (C) External search is futile; explore the inner space for answers.}}
\]