Option (D). All statements are true.
Horizontal micro programming:
1) Each control signal itself present in control word So no need of signal decoders, To represent one control signal we need 1-bit so A, C is true
2) In Vertical micro programming control word contain log(no of control signals) bits to represent control signals.
Ex: suppose 16 control signals are there, In HmP 16 bits, in VmP log16 = 4 bits are required
so B is true
Finally Option D is Answer