>If stability lock switch is turned off
If the question concerns autopilot type equipment, the controls will remain at last command input position whether set by hand or servo command. All controls function normally, stability gear engaged or otherwise (largely- there are exceptions to this very broad statement).
>A. Returns all trim commands to normal
>B. Returns cyclic stick to centre and keeps a/c at same attitude >and speed
Helicopters are always in the process of diverging from trim. All attitude and speed settings are temporary. You set the controls for configuration desired and then correct for changes as they occur.
>C. Returns cyclic stick to centre and keeps a/c at same attitude
See above- there is no useful "center" for controls except once landed. The trim switch, in most helicopters, doesn't change control rod length, it reduces felt control load. In a helo with boosted controls, that force is artificial and trimming changes the centering position of the springs creating control feel.
>1. What affect does parasitic drag have on the attitude of a >helicopter in flight.
Yes. That's the correct answer because "in flight" could be in any or no direction, except up...
The fuselage vector is below the thrust line, so aircraft response to forward cyclic is nose down and follows the disk. That's the way pilots think of it anyhow- the fuselage follows disk inclination. There are times and aircraft where this rule of thumb has exceptions, however. For instance, some aircraft pitch down in rearward flight configurations instead of nose up, as you'd expect. The tendency is startling the first time you encounter it, but one continues to direct the aircraft as desired as long as attitude doesn't continue to diverge.