Which of the following do physicists believe are fundamental particles?

a.

three quarks and three leptons

c.

three quarks and six leptons

b.

six quarks and three leptons

d.

six quarks and six leptons

The correct answer would be D. Physicists believe that the fundamental particles are six quarks and six leptons. These terms are used in particle physics and is known as the fundamental particles together with antiquarks and antileptons. The substructure of these particles are still unknown.