Although Maya usually _____ (work) alone, this week she _____ (collaborate) with three classmates.
works / is working
A habitual action contrasts with a temporary situation.
By the time we _____ (reach) the cinema, the film _____ (already / start).
reached / had already started
The film started before the later past event.
Correct the error: 'I am knowing exactly what you mean.'
I know exactly what you mean.
Know expresses a state and is not normally used in the continuous form.
Find and correct the error: 'I have finished my homework two hours ago.'
I finished my homework two hours ago.
Ago specifies a completed past time, requiring past simple.
I _____ (read) three chapters so far, but I _____ (not understand) the author's main argument yet.
have read / haven't understood
Both describe experiences or results up to the present. Understand is stative.
While the journalist _____ (interview) the actor, someone suddenly _____ (interrupt) them.
was interviewing / interrupted
An ongoing past activity was interrupted by a shorter event.
Complete: 'I _____ (think) your explanation is convincing, but I _____ (think) about another possible solution right now.'
think / am thinking
Think means believe in the first clause and consider in the second.
Complete: 'It's the first time I _____ (drive) such a powerful car.'
have driven
It's the first time is normally followed by the present perfect.
This is the third time our teacher _____ (explain) the rule, yet some students still _____ (make) the same mistake.
has explained / are still making
Present perfect follows 'This is the third time'; present continuous emphasises repeated behaviour that is continuing.
The road was flooded because it _____ (rain) heavily for several hours before the storm finally _____ (stop).
had been raining / stopped
Past perfect continuous highlights the duration and explains the past result.
Correct the error: 'She has been owning the company for ten years.'
She has owned the company for ten years.
Own is stative in this meaning, so the present perfect simple is appropriate.
Correct the sentence: 'By the time I had arrived, the meeting already started.'
By the time I arrived, the meeting had already started.
The arrival is the later past event; the meeting started earlier.
Why _____ you _____ (smell) the milk? It _____ (smell) perfectly fine to me.
are you smelling / smells
Smell is an action in the first question and a perception or property in the second.
I _____ (never / see) him so nervous before he _____ (give) his first public speech last year.
had never seen / gave
The experience is viewed from a point in the past, before the speech.
Complete: 'The chef _____ (taste) the sauce when he suddenly realised that it _____ (taste) too salty.'
was tasting / tasted
The first refers to a deliberate action in progress; the second describes flavour.
Complete: 'I _____ (wait) for nearly an hour when I suddenly _____ (realise) that I _____ (leave) my phone at home.'
had been waiting / realised / had left
Duration before a past moment, sudden realisation, and an action preceding that realisation.
Ever since the new manager took over, employees _____ (complain) about the workload, and several _____ (already / resign).
have been complaining / have already resigned
Since marks the starting event; present perfect continuous stresses ongoing complaints, while present perfect simple counts completed resignations.
When the police _____ (arrive), the suspect _____ (escape), but his accomplice _____ (still / hide) inside the building.
arrived / had escaped / was still hiding
Three past time relationships: arrival, earlier escape and action in progress at arrival.
Complete: 'I _____ (see) the dentist tomorrow, but I _____ (not see) why I should cancel my meeting. I _____ (have) this appointment booked for weeks.'
am seeing / don't see / have had
See is an arrangement, then understand; have expresses possession of an appointment extending to the present.
Complete: 'I _____ (always / believe) that he was honest until I _____ (discover) that he _____ (lie) to us for months.'
had always believed / discovered / had been lying
A previous belief ended at discovery; lying continued over a period before discovery.