Ascientist discovered an elementary particle paired with another particle. it has a positive charge equal to two–thirds of the charge of an electron. how should the scientist categorize the particle?

a.) boson

b.) lepton

c.) photon

d.) quark

W boson has +1e or - 1e charge, Z boson has 0 charge.

Leptons have +1e, -1e or 0 charge.

Photons have 0 charge.

Only quarks have a charge of +2/3e or -1/3e of an electron charge. 

To be exact, only up-type quarks (Up, Down and Top quarks) have a +2/3e or two thirds of an electron charge.

So the correct answer is D) Quark.