The man (who-that) robbed the bank had two pistols.
The bag (which-that) contained the money is yellow
ارجو كتابه القاعده

تستخدمwho لتحل محل الفاعل العاقل.بينما تستخدم whichلتحل محل غير العاقل وتستخدم that بدلا من whoاو which اى ان that = who \whichفى الاستخدام

the probleme not choosing who or that but the probleme we want to egyptanize every thing to make the language more difficult let's learn how to speak fluently not how to anser fluently.