Organic Nomenclature

Which is the correct name?

2-ethyl-2methylbutane 3,3-dimethylpentane
Incorrect
Choose the longest C chain
Correct
2-dichlorobutane 2,2-dichlorobutane
Incorrect
Each substituent must have a number
Correct
1,1-difluoro-3-nitrobutane 2-nitro-4,4-difluorobutane
CorrectIncorrect
Minimize the numbers