Cette pomme est bonne. - Oui, c'est bon.

Question

This was asked 4 years ago and never answered.
"This apple is good. Yes, it is good." is the stated English translation.
Had the English translation been "Yes, THEY are good", then "c'est bon" may be correct.
But, as stated, since IT is specific and refers to THIS APPLE, the French should be "Oui, elle est bonne."

Accepted Answer

Bonjour David,
You are correct that this test question is not right. Thank you for pointing it out! It has now been amended accordingly and we've added an example in the lesson to illustrate this point too.
I hope this is helpful.
Bonne journée !

Answer

In current usage, “ c’est bon “ is very common, colloquial French in this situation. (See attached link under discussion point 4, and the examples further down in the discussion).

Of course, ‘ Elle est bonne ‘ is still correct too. There is no difference in the English translation of ‘ elle est bonne ‘ and ‘ c’est bon ‘ in this situation.

The question attached to the lesson you linked is not asking whether to use ‘ c’est ‘ or ‘ elle est ‘.

Regardless of whether ‘ c’est bon ‘ is “ Le bon usage “ or not, you will hear it commonly in everyday speech, but it will never be ‘ c’est bonne ‘ and that is the point of this lesson. (Likewise it will never be ‘ Elle est bon ‘ either).

https://www.frenchtoday.com/blog/french-grammar/cest-versus-il-elle-est/