How Does a Magnetic Field Affect a Charged Particle's Motion?

[vsage]

Another magnetism question

A particle of mass 7 kg carrying a charge of 82 micro-Coulombs enters a uniform B field of intensity 9 T at a speed 92 m/s and at an angle of 25° with respect to the field lines as shown in the figure. (Positive y is up positive x is right the field is pointing in the positive x direction and positive z is coming out of the screen)

True/false

A) The field does a finite amount of work on the particle as the particle's trajectory is bent by the field.
B) The x-component of the particle's velocity is unchanged as it passes through the B-Field.
C) The Force on the particle is in the -z direction.
D) The particle follows a helical path.
E) The particle's speed varies as it passes through the B-Field.

I got these answers:
A. True Work = Fcos(theta) and theta is always 90 degrees
B. False magnitude of speed is always the same but direction changes
C. True - right hand rule
D. True - Force is negative z direction but acts circularly in the plane of the field
E. False - Speed can't vary since the force acts perpendicular to the velocity.

Which ones did I get wrong?

 

[vsage]

I uploaded a picture of the drawing here:

http://www.geocities.com/vsage3/magnetism.bmp

 

[Tide]

Regarding (A), how can the field do work if the force is perpendicular to the direction of movement?