What is the difference between "talk" and "say"?

[Guest]

Test No. errors/inter-5 "Talk about it later", question 3

I would rather not discuss the matter now but I'll say about it later.

(a) rather not
(b) matter
(c) say
(d) later

Test No. errors/inter-5 "Talk about it later", answer 3

I would rather not discuss the matter now but I'll talk about it later.

Correct entry: talk
The error was: (c) say
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talk not say

[Mister Micawber]

.
Yes, that is correct: talk, not say. The keys are the preposition about (which say does not take as a two-word verb), and the lack of an object (which say requires).
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Native English teacher at Mister Micawber's