What part of a check is the least important? a. the check number b. signature line c. memo line
d. routing number

Memo line  

Explanation:

The components of a check are:  Account number, check number, numerical amount, routing number, written amount, memo line, signature line

The most important parts of a check are:  The check number as it recognizes the check and the account number identifies the account whilst the signature gives the authorization. The routing number is important because it indicates which establishment issued the check

However,  Memo line is the least important since it is an optional field.