Learn Spanish (Latin America): ¿Quién puede explicar el problema?

Quién means "who." When we ask a question about an unknown single person, we treat quién exactly like "he" (él) or "she" (ella). Because of this, we use the third-person singular form of the verb, which is puede.

Why is explicar not conjugated here?

This is how Spanish handles two verbs working together. When you use a verb like poder (can / to be able to) to talk about an ability, only the first verb gets conjugated (changed to match the subject, like puede). The action verb that follows it stays in its original dictionary form (the infinitive), which is explicar here.

Do I need a connecting word like a or que between puede and explicar?

No! Unlike some other verb pairs you might know—like tener que (to have to) or ir a (to be going to)—the verb poder connects directly to the next verb. You just put them side by side: puede explicar.

Wait, shouldn't words ending in "-a" be feminine? Why is it el problema?