What is the difference between appeared and supposed?

[Thameem]

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #84 "Improving Verbal Skills", question 9

She ......... to be very confident on stage but inside she was feeling very nervous.

(a) appeared
(b) supposed
(c) stood
(d) credited

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #84 "Improving Verbal Skills", answer 9

She appeared to be very confident on stage but inside she was feeling very nervous.

Correct answer: (a) appeared

Your answer was: incorrect
She supposed to be very confident on stage but inside she was feeling very nervous.
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why appeared instead supposed? Please explain

[Mister Micawber]

'Supposed' would need to be preceded by 'was'.
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Native English teacher at Mister Micawber's