Tornadoes occur throughout the world

[Volcano1985]

Tornadoes occur throughout the world, but for reasons scientists are not fully able to -------, the great majority occur in the USA.

A) adopt B) allot C) sustain D) discern E) yield

I think D

[emsr2d2]

Tornadoes occur throughout the world, but for reasons scientists are not fully able to -------, the great majority occur in the USA.

A) adopt B) allot C) sustain D) discern E) yield

I think D

And you are right. Do you know why it's D? Or, more to the point, why it is not A, B, C or E?

[5jj]

Of the answers on offer, D is the one that is not impossible, though it is not very natural.

[Volcano1985]

And you are right. Do you know why it's D? Or, more to the point, why it is not A, B, C or E?

Yes, I know why it is D, because the key is C

[Tdol]

C doesn't work for me- how can you sustain reasons you don't know?

[Rover_KE]

A better answer would have been explain.

Rover