[单选题]
A beam of electrons entes 2s+slxfb0c fjvf/61 :gd up+rs a uniform electri8 ;yt.f, 0nz jdhaq b2lnd8fw7c 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