Screwballs,
Personally, I would have said A and C are both correct but given that you can't choose both of those there isn't really a correct answer!! Maybe a typo on behalf of the question setter for answer 'D' perhaps?!
TR4A,
This is from memory and not from the manual but I believe that the action of pulling the reverser handles from their stowed position raises a 'switch' that lifts the speedbrake out of its down detent thereby deploying it. I think
Funny one!
TS6