Gray iTunes album tracks

I noticed that a few tracks from an album appear gray.

The tracks are downloaded, I can play them if I double click them explicitly, but they don't play as part of the album. If I click the album's "play" button, they're skipped (1 gets played, then 3, then 4, etc.)

Why is this happening and how can I prevent it?

I saw a similar question, Grayed-out tracks in iTunes library, but that's not what I'm experiencing — for me, the songs do get downloaded and everything appears to be OK, they just get skipped when playing the album.

Solution 1:

If you view by Songs rather than Albums, you'll see they are unchecked.

iTunes will always skip unchecked songs, by default.