In the given sentence, fill in the blank with the correct preposition.
You should pay careful attention ______ what the speaker is highlighting.

Correct option is D

The correct answer is (d) to.
In the sentence, the verb phrase pay attention is followed by the fixed preposition to. Hence, the correct construction is pay attention to what the speaker is highlighting.
• Grammatical rule involved (English):
Certain verbs and noun phrases take fixed prepositions. The standard collocation is pay attention to, not with/from/for.
• व्याकरण नियम (Hindi):
कुछ verb phrases के साथ निश्चित preposition ही प्रयोग होती है। Pay attention के साथ हमेशा to का प्रयोग किया जाता है।
• Meanings / role of the other options:
• (a) with: Not used with pay attention.
• (b) from: Incorrect preposition for this phrase.
• (c) for: Does not fit the fixed collocation.
Thus, the correct option is (d) to.