Two charged point particle are located at two vertices of an equilateral triangle and the electric field is zero at the third vertex. we conclude: a) the two particles have charges with opposite signs and the same magnitude b) the two particles have charges with opposite signs and different magnitudes c) the two particles have identical charges d) the two particles have charges with the same sign but different magnitudes e) at least one other charged particle is present

Option E

Explanation:

In the presence of two point charges at the two vertices of an equilateral triangle, the resultant electric field at the third vertex due to these charges can not be zero whether the charges are identical or not.

The reason being that only of the x or y component of the field can be cancelled out in either case still the total field can't be reduced to zero.

This can only be achieved if another charge is present.

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c) both a and b.