Which statement is not true of the nucleus?
a.) enclosed by a single membrane.
b.) materials pass in and out through pores in the membrane.
c.) present in eukaryotes but not archaea.

A.) Enclosed by a single membrane.

Explanation:

When we classify the organisms that live on this planet, we make a distinction between those that have a nucleus, which are called eukaryotes, and those that have no nucleus, which we call prokaryotes. The nucleus contains all the genetic material of a eukaryotic cell, but this genetic material needs to be protected. And it is protected by the nuclear envelope, which is a double membrane that surrounds all nuclear genetic material and other core components. In the nuclear envelope there are small holes or pores that allow messenger RNA and proteins to move between the nucleus and the cytoplasm. But what the nuclear membrane regulates is what material must be in the nucleus, and not what material must be in the cytoplasm.

The nuclear envelope is a double membrane that delimits the nucleus of the cell. It serves to separate the chromosomes from the rest of the cellular content. The nuclear envelope appears to be crossed regularly by small perforations or pores that allow the passage of certain materials, such as ribonucleic acids and proteins, between the nucleus and the cytoplasm.