What is the antecedent of pronoun in sentence Listening attentively a valuable skill Students should train themselves to do it effectively?

The antecedent of the pronoun "it" in the sentence "Listening attentively is a valuable skill. Students should train themselves to do it effectively" is "listening attentively".

Here's why:

* "Listening attentively" is the subject of the first sentence and is a noun phrase.

* "It" in the second sentence refers back to the action of "listening attentively".

Therefore, the antecedent of "it" is the noun phrase "listening attentively".