Is it grammatically correct to use 'a' in the following sentences? (see bold parts)
The author calls them elitist because of their belief that someone without a formal education could never have written the masterpieces ascribed to Shakespeare.
But did you know that it takes the bald eagle five years to grow into one with a distinctive plumage?
I found these sentences in a practice paper for grammar correction. They didn't use 'a' in any of these sentences and didn't even mention them in the correction. So now I'm wondering about this.