Choose the best description of an electron.

a. A sub-atomic particle of insubstantial mass that determines an atom's positive charge.
b. A sub-atomic particle of considerable mass that determines an atom's positive charge.
c. A sub-atomic particle of considerable mass that determines an atom's negative charge.
d. A sub-atomic particle of insubstantial mass that determines an atom's negative charge.

d. A sub-atomic particle of insubstantial mass that determines an atom's negative charge.