"expand on" versus "spread out"

[Ljiljan Maksimovich]

English Grammar Tests, Elementary Level

ESL/EFL Test #88 "Common English Errors (4)", question 8

His speech was articulate and I asked him to ......... his ideas.

(a) make bigger
(b) spread out
(c) expand on
(d) expand about

English Grammar Tests, Elementary Level

ESL/EFL Test #88 "Common English Errors (4)", answer 8

His speech was articulate and I asked him to expand on his ideas.

Correct answer: (c) expand on

Your answer was: incorrect
His speech was articulate and I asked him to spread out his ideas.
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Why not spread out?

Ljiljan

[Alan]

Hi Ljiljan,

Spread out doesn't really work here because it is usually used literally to mean display fully. You could have a large map in a roll and you want to see it as a whole and so you lay it on a table and spread it out so that all four corners are flat.

Alan
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[Farzana]

What does it mean "expand on"

Farzana

[Kitosdad]

To give further ideas and explanations to reinforce your claims.
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