The following sentence has been split into four segments. Identify the segment that contains a grammatical error. By the end of / this month, he / will been working / for five years.

Correct — A. The segment prints will been working, and no English tense has that shape.

The trigger is By the end of this month ... for five years — a stretch of time running up to a point in the future. That is the future perfect continuous, and its form is fixed: will have been + V-ing.

Corrected: By the end of this month, he will have been working for five years. The error sits in option (a).

Why the others are wrong

• (b)
  By the end of — By the end of is a complete prepositional phrase and the ordinary marker of a future deadline. It fixes the point the tense must reach, and nothing inside it is misformed.
• (c)
  this month, he — this month, he is a noun phrase plus a subject pronoun, with the comma closing the fronted time phrase. Singular he agrees with any correctly built verb that follows.
• (d)
  for five years — for five years is the right duration phrase: for takes a length of time, since takes a starting point. This five-year span is what forces the continuous, not what breaks it.

A spot the error item hands you four segments and exactly one fault, so read for form rather than for sense.

The fastest filter is the auxiliary chain. English builds a verb phrase in a fixed order — modal, then have, then be, then the main verb — and each link dictates the form of the next: will takes a bare infinitive, have takes a past participle, be takes the -ing form.

will been working breaks the chain at its first link, because been is a past participle standing where a bare infinitive belongs. Put have back and the chain is legal.

Key facts

• The future perfect continuous is formed will have been + V-ing, a fixed four-part chain.
• A modal such as will, shall, can or must is always followed by a bare infinitive, never by been.
• By + a future time point names the deadline a perfect tense reaches, as in by the end of this month.
• For measures a length of time, as in for five years, while since marks a starting point.

Common traps

• Reading the segment for meaning, where will been working still sounds like a plan, instead of testing its form.
• Marking for five years wrong because a five-year span feels as though it needs since.
• Repairing it to will have worked, which is grammatical but drops the ongoing sense the duration carries.

No directly related past PYQ was found.