1. Whatever you choose will be the right decision for you. (Noun clause as the subject of the sentence)
2. I understand why you're feeling so stressed. (Noun clause as the object of the verb "understand")
3. The teacher explained how to solve the problem. (Noun clause as the object of the preposition "how")
4. That you're here means a lot to me. (Noun clause as the subject of the sentence)
5. Whether you succeed or fail depends on your effort. (Noun clause as the subject of the sentence)