I have been waiting here <u>for</u> the last two hours.
- (a)from
- (b)since
- (c)by
- (d)NO IMPROVEMENT
Answer
Why
Correct: D, NO IMPROVEMENT. 'The last two hours' names a stretch of time rather than a moment, and English marks a stretch with 'for', so the sentence as printed is already right: 'I have been waiting here for the last two hours.'
Why the others are wrong
- (a)from: 'From' announces a starting point and normally expects a matching 'to' or 'till'; it is not used with a perfect tense to measure how long something has gone on.
- (b)since: 'Since' has to be followed by the point at which the period began, such as 'since four o'clock' or 'since Monday', not by the length of the period.
- (c)by: 'By' fixes a deadline: 'by six o'clock', and says nothing about duration, so it cannot govern 'the last two hours'.
Concept
'For' measures how long a period lasted; 'since' names the moment it started.
Every option here is a preposition of time, so the item is really a single question asked four ways: does 'the last two hours' name a length or a moment. It names a length, and that settles it in one step. Items of this kind are also a reminder that in a sentence-improvement set the printed sentence is sometimes already correct, and a candidate who assumes there must be a fault will change a right answer into a wrong one.
Key facts
- 'For two hours' states a duration; 'since two o'clock' states a starting point.
- The present perfect continuous is the usual tense for an action that began earlier and is still going on.
Study next
Common traps
- Assuming that the underlined part must be faulty because it has been underlined.
- Using 'since' before a length of time instead of before a point in time.
Asked as a sentence-improvement item on time prepositions, with a correct sentence and three plausible-looking substitutions.
Related PYQs
Years _____ since I saw her last.
- (a) have passed
- (b) had passed
- (c) had been passing
- (d) have been passing
Answer(a) have passed
The same family of time expressions. That NDA item turns on what tense 'since' pulls after it once a starting point has been named; this one turns on the choice between 'since' and 'for' when the time expression is a length rather than a point.
Practice
- practice, not a real PYQ
Which option best improves the underlined part: She has been unwell <u>since</u> the last three days.
- (a)for
- (b)from
- (c)by
- (d)No improvement
Answer(a) for: 'the last three days' is a length of time, so it takes 'for'. - practice, not a real PYQ
Which option best improves the underlined part: They have been living in Pune <u>for</u> 2010.
- (a)since
- (b)from
- (c)by
- (d)No improvement
Answer(a) since: a year names the point at which the period began.