Which of these particles is classified as a lepton?
(a)-electron
(b)-proton
(c)-neutron
(d)-photon
(e)-boson

(A)-electron

Explanation:

Particles can be classified into:

- Leptons: particles which do not feel the strong interaction

- Hadrons: particles which interact by strong nuclear forces (they are actually not fundamental particles, since they are composed of quarks)

- Boson: the mediators of the four fundamental forces

The given options in this problem are:

(A)-electron  --> LEPTON (because it does not feel the strong interaction)

(B)-proton  --> HADRON (it consists of quarks)

(C)-neutron  --> HADRON (it consists of quarks)

(D)-photon  --> BOSON (it is the mediator of the electromagnetic force)

(E)-boson --> BOSON

So, the only lepton among the choices is (A) electron.

the first, second, and fifth options