1.Select the correct sentence:

A) The node which was 3 mm was excised.
B) The node which was 3-mm was excised.
I answered B
2. Select the correct sentence:
A) The doctor excised the 3 mm node.
B) The doctor excised the 3-mm node.
I answered B

1. is A. Please read the link I posted about hyphens.

sorry I meant A for 1 and B for 2. :/ sorry about that

For both questions, you have selected option B as the correct sentence, and you are correct!

In question 1, the correct sentence is "The node which was 3-mm was excised" (option B) because when using hyphenation to combine a measurement (3 mm) with a noun (node), it is important to include the hyphen between the measurement and the noun.

In question 2, the correct sentence is "The doctor excised the 3-mm node" (option B). Again, the hyphen is used to combine the measurement (3 mm) with the noun (node).

So, your choices of B for both questions are correct because they include the necessary hyphen between the measurement and the noun in each sentence. Well done!