Also it should be noted that Ols' sentences are wrong as well. The original statements were past tense, not present. Can I borrow your time machine?
:CIsee:I still want your time machine.
And Watson solving a case?:CShock: I laugh slowly twice then wait quite a while before giving a third laugh.
I'm not sure about pluralization. While it might be singular for your reasons, there are multiple subjects given. Also, in neither-nor, both Holmes and Watson have failed to solve the case.
What about an 'or' that leaves open the option for more than one to do it.
for example: Let me know if either Jesse or James (have?) shown any competance.
I think 'nor' might be have as well, since it can easily be written as "both X and Y have not done A"
Then you can tell your teacher that they're both wrong in English. 'Nor' follows 'neither' and 'or' follows 'either'.
It's neither:
"Either Holmes nor Watson will solve the case"
nor is it:
"Neither Holmes or Warson will solve the case"
It's either:
"Either Holmes or Watson will solve the case"
or it's:
"Neither Holmes nor Watson will solve the case"