An electron moving along the +x-axis enters a magnetic field. If the electron experiences a magnetic deflection in the -y direction, what is the direction of the magnetic field in this region?

Into the page (negative z-axis)

Explanation:

We have a charge moving towards the left (as it is an electron we reverse the direction.)

We have an output motion downwards.

We know that the magnetic field would be in to both direction of charge and motion.

Using Fleming's Left Hand Rule.

Thumb for direction of thrust. (Downwards)

Field for direction of magnetic field (unknown)

Middle finger for direction of current (To the left)

We can determine that the magnetic field would be going into the negative z axis.

the entire statement is true and correct.  

there's no diagram, nothing is illustrated, and no question is asked.