Part of the reason for...

[Tan Elaine]

Part of the reason for his failing the exam is laziness.

Is the part in bold correctly used?

Thanks.

 

[Tdol]

It's OK, but I would say his laziness.

 

[Rover_KE]

Also, I'd say 'One of the reasons...'

 

[Tan Elaine]

What I don't understand is why "Part of the reason..." is correct when there should be at least one reason for something to happen. Is it idiomatic?
"One of the reasons..." makes more sense to me.

Could someone please let please comment on this? Thanks.

 

[Tdol]

There could be a single reason, of which the laziness was a part- the rest would be related. However, I agree with Rover that one sounds better.