[单选题]
A beam of electrons enta1/7yi)xsqob 3 mjc6jers av 5rvp u.)-qqz uniform electric field, as shown.
What effect does this field have on the horizontal and vertical components of the electrons' velocity?
A. Horizontal velocity is Increases ; Vertical velocity is Stays the same
B. Horizontal velocity is Decreases ; Vertical velocity is Stays the same
C. Horizontal velocity is Stays the same ; Vertical velocity is Increases
D. Horizontal velocity is Stays the same ; Vertical velocity is Decreases