In X-ray lithography, if S is the size of the X-ray source, g is the gap between wafer and mask, and D is the distance between the source and the mask, then the blur is

• A. \(\frac{D}{{gS}}\)
• B. \(\frac{{gS}}{D}\)
• C. D - gS
• D. \(\frac{{g - D}}{S}\)