Boost vs heighten vs lift

[micaelo]

In the following multiple-choice exercise:
The mailing list has done much to ... the numbers of people attending.
A lift B encourage C heighten D boost
I know the correct answer is "boost" but I was wondering what makes "lift" and "heighten" incorrect, as they also mean "increase". Thank you

 

[oregeezer]

I think your running into idiomatic phrases. As a life-long speaker of English I would choose "boost" as the most natural co-location. All of the words can be used, but the intructions probaly ask for "the best" expression.