I don't quite understand the answer for this item. - Departing aerodrome with servicable radar IFR by day flight has been given clearance for visual departure. For this clerance to be offerred the cloud base should have been above:
a 300AGL
b Either MSA or MVA or LSALT for the departure route.
c height required to permit flight in VFR
d MVA.

The answer given is d, but with the explination of "If cannot be offerred unlses cloud base is such that the pilot can maintain VMC below either MVA, MSA or route LSALT... Which I'd have thought meant option b is correct?

MVA (minimum vector altitude) is indicated on the controller's radar screen for various sectors around the aerodrome. The pilot has no access to MVA which would normally be lower than either MSA or LSALT. So the cloud base could be lower than MSA or LSALT but above MVA. If the controller offered you the clearance it is because he has determined that the cloud base will permit you to operate in VMC even though it is lower than MSA or LSALT.

I'm puzzled by this too. Looking up AIR ENR 1.1 para 2.5.2.1 it says that the cloud base must be "such that the pilot can maintain flight in VMC below the MVA or the MSA/LSALT". What does maintaining VMC require in this context? If we're departing a class C aerodrome, for example, doesn't VMC require 1000 ft vertical separation from cloud? Wouldn't that mean the cloud base has to be at least 1000 feet above the intended flight path? If the plan is to climb up to MSA, wouldn't that mean the cloud base must be MSA+1000 ?

I agree that the choices in that question could have been confusing. I have reworded them as follows.

Question No 3 [See AIP ENR 1.1 para 2.5.2.1]
You are departing a controlled aerodrome which has a serviceable radar facility, ILS, VOR, NDB and DME. The IFR flight by day has been given the choice of a visual departure. Which of the following applies for this clearance to be offered? -
(a) no cloud below 300 feet AGL
(b) no cloud below either MSA or MVA or LSALT for the departure route.
(c) no cloud below the height required to permit VMC
(d) VMC exists below MVA (minimum vector altitude).

As far as AIP ENR 1.1 para 2.5.2.1 is concerned, I can't make it say anything else. You must be able to climb to MSA, LSALT or MVA in VMC. In this case, the question said you were offered a visual departure by the controller so he/she would have been satisfied that you could climb to MVA in VMC.

The exception would be in Class D environment, where VMC requires only 500 feet vertically and 600 meters horizontally separation from cloud. VFR G Chapter 3 Page 207.