Difference between believe in and trust in

[Elka Cooper]

English Language Tests, Intermediate level

ESL/EFL Test #72 "How to encourage", question 7

I've watched a lot of young people try to make a success of it, but you're the only one I really ......... in.

(a) think
(b) trust
(c) hold
(d) believe

English Language Tests, Intermediate level

ESL/EFL Test #72 "How to encourage", answer 7

I've watched a lot of young people try to make a success of it, but you're the only one I really believe in.

Correct answer: (d) believe

Your answer was: incorrect
I've watched a lot of young people try to make a success of it, but you're the only one I really trust in.
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Hi
Please tell me what is the difference between "believe in" and "trust in"?
For example we say " In God we trust".

Thanks.

[Alan]