In VERTICAL MICRO-PROGRAMMING , control signals are stored in encoded form. .
now in the Question given there are 5 groups which contains mutually exclusive signals, i.e, they can be activated one at a time for a given group.
group 1=⌈log3⌉=2 (Number of input bits for decoder, given output
is number of control signals in given group)
group 2=⌈log7⌉=3
group 3=⌈log10⌉=4
group 4=⌈log12⌉=4
group 5=⌈log2⌉=1
Total bits required in vertical micro-programming =2+3+4+4+1=14
while in HORIZONTAL MICRO-PROGRAMMING ,we need 1 bit for every control signals
so, total bits required in Horizontal Micro-programming =3+7+10+12+2=34 bits
therefore, total bits saved = 34-14 =20 bits
Hence, C is answer :)