Subject-verb agreement

The rule. A verb must agree with its subject: a singular subject takes a singular verb; a plural subject takes a plural verb.

Rule 1: find the real subject. 'A contingent of troops posted to Jammu and Kashmir was airlifted.' The subject is contingent, not troops. 'Of troops' just describes it. So: was.

Ignore the words between the subject and the verb:

• 'The bouquet of flowers is beautiful.'
• 'A pair of shoes is missing.'
• 'The data collected by the researchers shows clear trends.'

Rule 2: each, one of, neither of, every are singular:

• 'Each of the participants has submitted.'
• 'One of the players was injured.'
• 'Neither of the statements is true.'

Rule 3: neither… nor / either… or. The verb agrees with the part nearest to it:

• 'Neither the teacher nor the students were aware.'
• 'Either the children or their guardian has to attend.'

Rule 4: collective nouns (battalion, group, convoy, jury, team) take a singular verb when they act as one:

• 'A battalion of soldiers stands at attention.'
• 'A group of cadets prepares for their drill.'

Rule 5: some words end in -s but are singular: 'Mathematics is an interesting subject.' Also: physics, news, economics.

The corrected passage: 'Each soldier salutes with pride while the commander and his assistants inspect the parade. The sound of marching feet echoes through the air as a group of cadets prepares for their drill. Meanwhile, a convoy of military vehicles passes by.'