The toal number of isomers including stereoisomers for 1,3-dimethly cyclohexane is:
A. (a) 2, cis and trans both optically inactive
B. (b) 3, one cis and two optically active trans froms
C. (c) 3, one trans and two optically active cis froms
D. (d) 4, two cis (optically active) and two trans (optically active)
