Does verb phrase "speak up" mean tell the truth?

[Hamster]

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #44 "Scandal", question 9

At last Mathew decided to speak ......... for himself and tell the truth.

(a) on
(b) to
(c) up
(d) off

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #44 "Scandal", answer 9

At last Mathew decided to speak up for himself and tell the truth.

Correct answer: (c) up
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Does verb phrase "speak up" mean tell the truth?

Hamster

[Mister Micawber]

.
No, 'tell the truth' means 'tell the truth'. 'Speak up' means 'speak without fear or hesitation.'
.
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Native English teacher at Mister Micawber's