When We Determine the Angular Resolution of an Interferometric Array $\theta$

When we determine the angular resolution of an interferometric array of radio telescopes using the formula $\theta$$\infty$ $\lambda$ /D, the variable D stands for the

A) diameter of the telescopes.
B) separation between the telescopes.
C) magnification of the telescopes.
D) number of telescopes.
E) focal length of the telescopes.