Listening is what I would pick.

Learn to actively listen to what people are saying, what they don't say, and, most importantly, what they mean.

This will serve you in any career, but software devs who can grok what is meant rather than what is said are especially valuable.

Why? Because so much of what we deal with are abstractions that can be slippery and mean different things to different people. Getting a firm grasp on everyone's meanings is crucial to bridging divides and delivering value.