Unless we ______ now we can't be on time.

• will start
• start
• starts
• will be starting
Correct Option: B  [ start ]

Remark:

The modern student _________ the importance of physical exercise.

• understood
• understand
• have understand
• understands
Correct Option: D  [ understands ]

Remark: singular subject (i.e student) takes singular verb (i.e understands).
Note: generally verb ends with "s" is singular.

Each of the students _______ given a task to complete.

• were
• was
• have
• have been
Correct Option: B  [ was ]

Remark: If a subject is modified by the words "each" or "every" that subject is singular and will take a singular verb.

Every girl and every boy ________ given a silver medal.

• are
• was
• has
• have
Correct Option: B  [ was ]

Remark: If a subject is modified by the words "each" or "every" that subject is singular and will take a singular verb.

While eating he _______ a lot.

• talk
• talks
• talked
• taking
Correct Option: B  [ talks ]

Remark: Singular subject takes singular verb.

The horse and the coach ________ arrived.

• have
• have been
• would
• has
Correct Option: A  [ have ]

Remark: When two singular nouns joined by "and" refer to the same person or thing, the verb is singular.
But here article "the" used twice before each noun to indicate two different subjects, thus "have" used.

Most of the labourers _____________ on the strike.

• is
• has
• are
• have
Correct Option: C  [ are ]

Remark:

That woman ____________vegetables.

• sells
• sell
• have sold
• selling
Correct Option: A  [ sells ]

Remark:

This magazine _________ twice weekly.

• is appearing
• appearing
• appears
• appeared
Correct Option: C  [ appears ]

Remark: Subject is "Magazine" a Singular noun, go with singular verb.

Each of the students ________ responsible for keeping this room clean.

• are
• has
• is
• have
Correct Option: C  [ is ]

Remark: