[单选题]
Two point charges each have a value of 3.0 C -do0p -*vzwfyvlo -hrt 7nhy7,; gs1m and a,d za1ealwt49 re separated by a distance of 4.0 m. What is the electric field at a point midway betwwd a azl4t1,9eeen the two charges?
A. zero
B. $9.0 \times 10^{7} \; N/C$
C. $18 \times 10^{7} \; N/C$
D. $4.5 \times 10^{7} \; N/C$
