In the steps leading up to the origin of life on earth, early protobionts could not have evolved into living cells without both:

Explanation

Early protobionts, which were simple, non-living structures, needed two critical developments to evolve into true living cells. First, they required A semipermeable membrane to maintain a distinct and stable internal environment separate from the external environment, allowing for concentration of specific molecules. Second, they needed the ability to catalyze chemical reactions (metabolism) in a controlled way, which would have been achieved by early ribozymes or proteins. This controlled, contained metabolism is the definition of a simple, self-sustaining life form. The nucleus (Option D) evolved much later, and competition (Option B) is a force of selection, not a prerequisite for the cell's basic functionality.