The answer "nonpolar" is incorrect because polar water molecules can actually pass through the plasma membrane easily. The correct answer is "polar."
To understand why, let's take a look at the structure of the plasma membrane. The plasma membrane is made up of a phospholipid bilayer with hydrophobic (water-hating) tails and hydrophilic (water-loving) heads. The hydrophilic heads face the extracellular fluid and the cytoplasm, while the hydrophobic tails are sandwiched in between.
Since water is a polar molecule, its hydrophilic nature allows it to interact with the hydrophilic heads of the plasma membrane. This enables water molecules to pass through the membrane easily, which is essential for many cellular processes.
If you still have doubts or need further clarification, it's always a good idea to visit your professor during office hours. They can provide valuable insights and explain the correct answer in detail. Additionally, you can refer to the provided links for more information and resources on this topic.