Choose the part of the following sentence that contains an error:

If a company sends its employees abroad to work for a foreign client, they pays them a daily allowance.

The correct option that contains an error is: "Pays them a daily allowance".

To understand why this is the correct choice, let's break down the sentence structure and examine the pronoun-verb agreement:
The sentence is: "If a company sends its employees abroad to work for a foreign client, they pays them a daily allowance."

First, let's identify the subject and pronoun reference in the main clause:
The main clause starts with "...they pays them a daily allowance."
Here, the pronoun "they" is used to refer back to the plural noun "employees" (who are receiving the payment) or is meant to represent the company/management in a collective plural sense. Since "they" is a plural pronoun, it must agree with a plural verb form.

Second, let's look at the verb conjugation:
The verb used in the option is "pays", which is a singular verb form (used with he, she, or it).
A plural pronoun like "they" requires the plural verb form "pay" instead of "pays".
Therefore, the phrase "they pays" contains a subject-verb agreement error. It should either be "they pay them..." or, to maintain consistency with the singular noun "a company", it could be written as "it pays them...". In either case, the segment "pays them a daily allowance" contains the grammatical error.