Isn't the "could" repeated incorrectly?

[Barry]

English Language Tests, Intermediate level

ESL/EFL Test #120 "Conditional Tenses", question 2

If they had waited another month, they could probably ......... a better price for their house

(a) would get
(b) had got
(c) have got
(d) could get

English Language Tests, Intermediate level

ESL/EFL Test #120 "Conditional Tenses", answer 2

If they had waited another month, they could probably have got a better price for their house

Correct answer: (c) have got
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isn't the 'could' repeated incorrectly? Could probably have gotten.

Barry

[Alan]

Hi Barry,

I'm not clear what you mean. What's the difference between my version:

could probably have got and yours:

isn't the 'could' repeated incorrectly? Could probably have gotten.

??

Alan
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English as a Second Language
You can read my ESL story A day in the life of a flat hunter