A is smaller than B but not than C. Than is not necessarily required for the sentence to make sense. 'than' is a comparative function to compare two or more things so it that is why it is also acceptable in this sentence. An alternative would be: A is smaller than B, but not smaller than C or: A is smaller than B, but not C. Feel free to message me if you have any further questions

The correct answer is: A is smaller than B but not C. You use 'than' once only. If you added items you would use 'or' to set them off. Megan's two alternatives are good, too.

Hi there Hiro, The 'than' is not necessary before 'C'. In fact it sounds quite strange to include it. I think the sentence is written pretty well! The only thing I would change in it is to maybe write the sentence first, because it looked a bit strange at first sight. Maybe you could say: In the sentence "A is smaller than B but not than C" is it necessary to include 'than' before 'C'?