When you have the word 'and' in your subject, is it always plural? No, not always.
"Peanut butter and jelly is available in the cafeteria," and "Meat and potatoes was my grandfather's favourite meal."
In these sentences, the two items combine to form a single unit (one dish) and this is the crux of the matter. When the nouns form 'a collective idea' or 'a oneness of idea,' the singular verb is appropriate"
But sometimes it is not clear. How do you view the following?
"His humility and his decency reflects the very best of the Australian spirit."
To decide on singular or plural, we need to assess whether "his humility and his decency" are two variations on a theme and therefore one thing, or if these two personal qualities are "different and separable."
They seem like separate ideas to me. A person could be decent but not so humble. So I vote for singular. You may disagree.
So what's the solution?
If you come across this problem in your own writing, you'll probably make someone unhappy no matter which verb you choose - singular or plural.
Your best chance for pleasing everyone is to recast the sentence so that you no longer have to wrestle with the idea of singular or plural.
What about this:
"He embodies the very best of the Australian spirit with his humility and his decency."
Problem solved.
Always remember that rewriting is an option. In fact, most authors would say that rewriting is the essence of all good writing.
