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

Ex Input:
Passage: The Arrhenius definition of acids and bases is somewhat limited. There are some compounds whose properties suggest that they are either acidic or basic, but which do not qualify according to the Arrhenius definition. An example is ammonia (NH 3 ). Its aqueous solution turns litmus blue, it reacts with acids, and displays all the other properties of a base. However, it does not contain the hydroxide ion. In 1923, a broader definition of acids and bases was independently proposed by Danish chemist Johannes Brnsted (1879-1947) and English chemist Thomas Lowry (1874-1936). A Brnsted-Lowry acid is a molecule or ion that donates a hydrogen ion in a reaction. A Brnsted-Lowry base is a molecule or ion that accepts a hydrogen ion in a reaction. A hydrogen ion is commonly referred to as a proton, and so acids and bases are proton donors and proton acceptors respectively according to the Brnsted-Lowry definition. All substances that are categorized as acids and bases under the Arrhenius definition are also defined as such under the Brnsted-Lowry definition. The new definition, however, includes some substances that are left out according to the Arrhenius definition. Answer: acid

Ex Output:
Which type of substance is considered a proton donor in a reaction?

Ex Input:
Passage: The male gametophyte produces flagellated sperm that must swim to the egg formed by the female gametophyte. For this reason, sexual reproduction must happen in the presence of water. Therefore, nonvascular plants tend to live in moist environments. Though the life of a nonvascular seedless plant is a cycle, this can be considered the initial step in the life cycle. Answer: water

Ex Output:
When flagellated sperm must swim to the egg, sexual reproduction requires the presence of what substance?

Ex Input:
Passage: Chapter 12 1 MRI uses the relative amount of water in tissue to distinguish different areas, so gray and white matter in the nervous system can be seen clearly in these images. 3 Neurons enable thought, perception, and movement. Plants do not move, so they do not need this type of tissue. Microorganisms are too small to have a nervous system. Many are single-celled, and therefore have organelles for perception and movement. 5 Sodium is moving into the cell because of the immense concentration gradient, whereas potassium is moving out because of the depolarization that sodium causes. However, they both move down their respective gradients, toward equilibrium. 7 A second signal from a separate presynaptic neuron can arrive slightly later, as long as it arrives before the first one dies off, or dissipates. 9 C 11 D 13 B 15 B 17 A 19 C 21 C 23 A 25 B 27 D 29 B 31 D 33 A 34 Running on a treadmill involves contraction of the skeletal muscles in the legs, increase in contraction of the cardiac muscle of the heart, and the production and secretion of sweat in the skin to stay cool. 36 The disease would target oligodendrocytes. In the CNS, oligodendrocytes provide the myelin for axons. 38 Afferent means "toward," as in sensory information traveling from the periphery into the CNS. Efferent means "away from," as in motor commands that travel from the brain down the spinal cord and out into the periphery. 40 The cell membrane must reach threshold before voltage-gated Na+ channels open. If threshold is not reached, those channels do not open, and the depolarizing phase of the action potential does not occur, the cell membrane will just go back to its resting state. 42 EPSP1 = +5 mV, EPSP2 = +7 mV, EPSP 3 = +10 mV, IPSP1 = -4 mV, IPSP2 = -3 mV. 5 + 7 + 10 4 3 = +15 mV. Answer: organelles

Ex Output:
Many microorganisms are single celled and use what for perception and movement?