C

Because Yeongjin is fair game and Sanha happens to be the closest one to his favorite hyung to date.

Seoljun honestly isn’t the jealous type. Sure he may have his moments, but generally he’s laidback enough not to get jealous.

But of course, this rule doesn’t quite apply to a certain Lee Sanha.

Even though everyone is practically close with everyone else, and had their fair share of skinship, there’s no one who likes skinship as much as Sanha. Sanha constantly needs skinship and attention, be it from the other members or from Yeongjin.

Seoljun just doesn’t like it when Sanha decides to cling onto Yeongjin.

To date, Sanha is the closest to Yeongjin. They’ve known each other and have been friends for quite a while (though for how long Seoljun isn’t quite sure), and not to mention they’re the same age. Sanha is a serious threat for Seoljun’s standing in receiving Yeongjin’s affections.

Besides, Yeongjin doesn't like it when Seoljun plays with him as if he’s a squishy little doll, but doesn’t even utter a word of protest when Sanha does the same thing. It’s completely unfair!

Though, don’t get him wrong, he’s actually very fond of Sanha. He’s a good and fun hyung, and really doesn’t mind it whenever the younger members gang up to . He’s a lovable person and there really is no reason for Seoljun to hate Sanha.

Of course, this notion gets thrown out the window completely when he sees Sanha hugging a laughing Yeongjin. Again.