Collective nouns. Nouns that denote a unit take singular verbs and pronouns: class,committee, crowd, family, group, herd, jury, orchestra, team.
Examples: The committee is meeting to set its agenda. The jury reached its verdict . A herd of cattle was sold.
Plural in form: Some words that are plural in form become collective nouns and take singular verbs when the group or quantity is regarded as a unit,
Right: A thousand bushels is a good yield. (A unit.)
Right: A thousand bushels were created. (Individual items.)
Right: The data is sound. (A unit.)
Right. The data have been carefully collected. (individually items.)
