Final answer:
Passive diffusion and osmosis are forms of passive transport where substances move across the cell membrane without any energy expenditure from the cell. Passive diffusion involves the movement of substances from higher to lower concentration, while osmosis is the movement of water across a semipermeable membrane.
Step-by-step explanation:
The process that occurs when substances cross the cell membrane automatically, without using any energy, can be described as passive transport. Among the options provided, Passive diffusion (D) and Osmosis (B) fall under this category. Passive diffusion is the movement of substances from an area of higher concentration to an area of lower concentration without the use of cellular energy. On the other hand, osmosis specifically refers to the movement of water across a semipermeable membrane from an area of higher water concentration to an area of lower water concentration. Meanwhile, facilitated diffusion is also considered a type of passive transport but involves the use of carrier proteins to move substances down their concentration gradient, and Active transport (A) requires energy in the form of ATP to move substances against their concentration gradient.