Question

Which of the following is true?

		Quarks appear in groups and leptons appear in groups.
		Quarks appear in groups and leptons are solitary.
		Quarks are solitary and leptons appear in groups.
		Quarks are solitary and leptons are solitary.

Which force is responsible for beta decay?

		The strong force.
		The electromagnetic force.
		The weak force.
		The gravitational force.

Which of these quarks is most stable?

		Top.
		Strange.
		Down.
		Up.

Answer 1

1) Quarks appear in groups and leptons are solitary.

Leptons and quarks are the two types of fermions. Leptons operate alone. Therefore they don't form groups. There are 6 types of leptons. eg: electron

Quarks are sociable and only exist in composite particles with other quarks. Quarks are also of 6 type eg: up, down etc

2) Weak nuclear forces causes the beta decay. In beta decay a beta particle is emitted from an atomic nucleus due to weak nuclear force.

3) Up and Down quarks are the lightest quarks and hence they are the most stable ones. Among those up quark is the lightest so most stable quark is up quark.