[单选题]
Two point charges each have a valuxjxk8a+on).m. bk+5vm 7yq 3qy,v ao be of 3.0 C and are separated e8-5b )zbv)q;kae n dvby a distance of 4.0 m. What is the electric field at a point midway be- ebkqd )vae8z;b 5n)vtween the two charges?
A. zero
B. $9.0 \times 10^{7} \; N/C$
C. $18 \times 10^{7} \; N/C$
D. $4.5 \times 10^{7} \; N/C$
