1. Oil is a natural resource. -- because "resource" is a singular countable noun, so needs an article or other determiner
2. I enjoy life. -- you enjoy life in general I enjoy the life. -- you enjoy a particular kind of life, or lifestyle, the nature of which is known from the context
3. A man handed me a bouquet of flowers. -- "some" feels
I think "the" is used when you refer to a specific already-known thing. You don't have to use an article when you mean something is universal. Ex, Coffee contains caffeine.
Thus, I don't get it when I see the following examples from my book.
1. The guests usually wait until the hostess begins to eat. Why there are "the" in front
1. "The guests ..." and "Guests ..." are both possible. The former means some specific guests (context-dependent). The latter means guests in general. "hostess" is a singular countable noun, so must have an article or other determiner.
2. "Brides ..." is also possible, meaning brides in general. However, it is more natural to follow it with "grooms" rather than "the grooms". Because the o