问

Don't confuse with

All three wrap something inside the door radical 门 — look at what's inside. 口 (mouth) inside 门 = 问 (wèn, to ask) — speaking through a doorway. 日 (sun) inside 门 = 间 (jiān, between/room) — light shining through the gap. 耳 (ear) inside 门 = 闻 (wén, to hear/smell) — listening at the door.