I'd use IS since both the words are singular (lack and plethora). g. the lack of money, the lack of time, etc, but I always wondered whether it's a right way to say or not.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
Grammar Geek"The lack of money is my checking account at this moment is a specific problem for me."Did you mean in?