Is this sentence acceptable?

[John Ting]

I have encountered a test question like this:

We can go there by/on this number of bus.

The question requires us to choose from by and on.

But it seems this sentence sounds stilted, whether a by or an on is used.

Please give me an explicit answer. Thanks!

[Clark]

I have encountered a test question like this:

We can go there by/on this number of bus.

The question requires us to choose from by and on.

But it seems this sentence sounds stilted, whether a by or an on is used.

Please give me an explicit answer. Thanks!

To go by bus - is a set-phrase
To go on a number 7 bus

[Soup]

The phrase this number of bus is awkward, which makes both on and by unacceptable:

Ex: We can go there on this number.
Ex: We can go there by this number.

Go (somewhere) by bus is a collocation.

We can get there on bus number XX.
We can get there by bus.