Given a scientific passage and an answer, generate a question for the given answer.

[Q]: Passage: The replacing of the electron enables chlorophyll to respond to another photon. The oxygen molecules produced as byproducts find their way to the surrounding environment. The hydrogen ions play critical roles in the remainder of the light-dependent reactions. Keep in mind that the purpose of the light-dependent reactions is to convert solar energy into chemical carriers that will be used in the Calvin cycle. In eukaryotes and some prokaryotes, two photosystems exist. The first is called photosystem II, which was named for the order of its discovery rather than for the order of the function. After the photon hits, photosystem II transfers the free electron to the first in a series of proteins inside the thylakoid membrane called the electron transport chain. As the electron passes along these proteins, energy from the electron fuels membrane pumps that actively move hydrogen ions against their concentration gradient from the stroma into the thylakoid space. This is quite analogous to the process that occurs in the mitochondrion in which an electron transport chain pumps hydrogen ions from the mitochondrial stroma across the inner membrane and into the intermembrane space, creating an electrochemical gradient. After the energy is used, the electron is accepted by a pigment molecule in the next photosystem, which is called photosystem I (Figure 5.13). Answer: hydrogen
[A]: What type of ions play critical roles in light-dependent reactions?

[Q]: Passage: Less dramatic types of mass wasting move Earth materials slowly down a hillside. Slump is the sudden movement of large blocks of rock and soil down a slope. ( Figure below ). All the material moves together in big chunks. Slumps may happen when a layer of slippery, wet clay is underneath the rock and soil on a hillside. Or they may occur when a river (or road) undercuts a slope. Slump leaves behind crescent-shaped scars on the hillside. Answer: slump
[A]: What is the term for the sudden movement of large blocks of rock and soil down a slope?

[Q]: Passage: Direction is just as important as distance in describing motion. For example, if Mia told a friend how to reach the post office from her house, she couldn't just say, "go 3 kilometers. " The friend might end up at the park instead of the post office. Mia would have to be more specific. She could say, "go west for 2 kilometers and then go north for 1 kilometer. " When both distance and direction are considered, motion is a vector. A vector is a quantity that includes both size and direction. A vector is represented by an arrow. The length of the arrow represents distance. The way the arrow points shows direction. The red arrows in Figure above are vectors for Mia's route to the school and post office. If you want to learn more about vectors, watch the videos at these URLs:. Answer: direction
[A]:
When describing motion, what factor is just as important as distance?