agreement between subject and verb

[Anonymous]

Dear teachers:

From a book I read following;
Recognizing recurring problems, alternative problem-solving approaches, avoiding common traps, managing time, and knowing how the computer calculates your final score is all part of your strategy.

Why the author uses singular verb? Can't we say "... are all parts of your strategy."? Is the author thinking that the subject is a single entity?

Thank you!

[Rusty]

Dear teachers:

From a book I read following;
Recognizing recurring problems, alternative problem-solving approaches, avoiding common traps, managing time, and knowing how the computer calculates your final score is all part of your strategy.

Why the author uses singular verb? Can't we say "... are all parts of your strategy."? Is the author thinking that the subject is a single entity?

Thank you!

Yes, I think the author is grouping these things together as one part of a large strategy, and there are other parts as well.