3. A quark cannot exist on its own, but must be bound to other quarks or an antiquark.
一个夸克不能单独存在，必须与其它夸克或反夸克结合在一起。
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4. Any of a family of subatomic particles that participate in strong interactions, are composed of a quark and an antiquark, and have masses generally intermediate between leptons and baryons.
介子任一种具有较强相互作用力的亚原子粒子群，由一夸克与一反夸克构成，并具有通常介于轻子和。
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5. Any of a family of subatomic particles that participate in strong interactions, are composed of a quark and an antiquark, and have masses generally intermediate between leptons and baryons.
