The correct answer is “in”.
“In” is the preposition that is most commonly used to express trust in someone or something. It can be used to describe a feeling of confidence or reliance on someone or something. For example, you might say “I have trust in my doctor” or “I have trust in the government”.
The other options are not as commonly used to express trust. “On” is often used to describe a physical location or position. For example, you might say “The book is on the table” or “The cat is on the chair”. “At” is often used to describe a time or place. For example, you might say “I’m meeting my friend at 10am” or “I live at 123 Main Street”. “Upon” is often used to describe a cause or reason. For example, you might say “The war was caused
by a dispute over territory” or “The building collapsed upon impact”.In the context of the question, “You must have trust in God”, the preposition “in” is the most natural choice. This is because the question is asking about a feeling of confidence or reliance on God. The other options do not convey the same meaning.