Positive and negative point charges of equal magnitude are kept at (0, 0, \[\frac{a}{2}\]) and [0, 0, \[-\frac{a}{2}\] ] respectively. The work done by the electric field when another positive point charge is moved from (-a, 0, 0) to (0, a, 0) is

• A. positive  
• B.                    negative  
• C. zero
• D. depends on the path connecting the initial and final positions