[单选题]
Two stars of equal ma j/lorven, bi23njma 8dg,, z/ss mqoa9y c7kn)n)(- tju$M$ are shown in the diagram, distance $d$ apart. A planet is equidistant from the two stars, with distance $\frac{d}{s}$ across the midpoint of the line joining the stars as shown.
What is the resultant gravitational field strength at the position of the planet due to the two star
A. $2\frac{GM}{d^2}\cos 45^{\circ}C$
B. $4\frac{GM}{d^2}\cos 45^{\circ}C$
C. $2\frac{GM}{d^2}\tan 45^{\circ}C$
D. $4\frac{GM}{d^2}\tan 45^{\circ}C$
