What does "shake on that" mean?

[Andy]

Business Idiom in English, Intermediate level

ESL/EFL Test #137 "Ways of agreeing", question 10

The ......... seem eminently suitable to me.

(a) tendencies
(b) actualities
(c) events
(d) terms

Business Idiom in English, Intermediate level

ESL/EFL Test #137 "Ways of agreeing", answer 10

The terms seem eminently suitable to me.

Correct answer: (d) terms

Your answer was: incorrect
The tendencies seem eminently suitable to me.
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what does "shake on that" mean??

Andy

[Mister Micawber]

.
Shake hands to seal that agreement.
.
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Native English teacher at Mister Micawber's