Afree positive charge released in an electric field will:
accelerate in the direction opposite the electric field.
accelerate along a circular path.
accelerate in the direction in which the electric field is pointing.
remain at rest.
accelerate in a direction perpendicular to the electric field.

accelerate in the direction in which the electric field is pointing.

Explanation:

The positive charge feels a force in the same direction as the electric field

F=Eq  

F and E are vectors, q is a scalar

(if it were a negative charge the force would be in the opposite direction)

that force will produce an acceleration in the same direction, that acceleration will cause the particle to move in the same direction, ie the direction of the electric field.

vapour or gas assuming atmospheriv pressure