Q: What element has the atomic number 16?    Choices:  - oxygen  - helium  - neon  - sulfur  A:
sulfur

Q: Channel proteins and carrier proteins help substances diffuse across what?    Choices:  - endoplasmic reticulum  - ribosomes  - cytoplasm  - cell membrane  A:
cell membrane

Q: What part of a plant protects the plant cell, maintains its shape, and prevents excessive uptake of water?    Choices:  - chloroplasm  - stem  - root  - wall  A:

wall