Q.30 Geometrical isomer (text Q3.6)

Which of (a) and (e) is the concise structural formula of 2-methyl-2-butene?
(a) CH3CBr=CHBr, (b) CH3CH2CH=CH2, (c) CH3CBr=CHCH2Br,
(d) CH3CH=CHCH3, (e)CH3CH=C(CH3)2.