[单选题]
Two point charges eac;ag mdi49s,o6a+vqi ch have a valuesnaqhf)omk5 h+kp.d19 -,hmf of 3.0 C and are separated by a distance of 4.0 m. What is the electric field at a point midway between the two chargeso fmd hq.-+phn5s,)af k k9hm1?
A. zero
B. $9.0 \times 10^{7} \; N/C$
C. $18 \times 10^{7} \; N/C$
D. $4.5 \times 10^{7} \; N/C$