[1] Which of the following alkane name is correct?  3,3-dipr…

[1] Which of the following alkane name is correct?  3,3-dipropylpentane, 2,3-dibutylpropane, 3-ethyl-4-methylbutane, 4-ethyl-5-butylheptane     [2] What is the correct IUPAC name for (CH3)2CH(CH2)3CH3? [3] What is the classification of this carbon (the one the arrow is pointing to)?