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

Q: Passage: In the nematic phase, only the long axes of the molecules are parallel, and the ends are staggered at random intervals. In the smectic phase, the long axes of the molecules are parallel, and the molecules are also arranged in planes. Finally, in thecholesteric phase, the molecules are arranged in layers; each layer is rotated with respect to the ones above and below it to give a spiral structure. The molecular order increases from the nematic phase to the smectic phase to the cholesteric phase, and the phases become increasingly opaque. Molecules that form liquid crystals tend to be rigid molecules with polar groups that exhibit relatively strong dipoledipole or dipoleinduced dipole interactions, hydrogen bonds, or some combination of both. Some examples of substances that form liquid crystals are listed in Figure 11.27 "Structures of Typical Molecules That Form Liquid Crystals*" along with their characteristic phase transition temperature ranges. In most cases, the intermolecular interactions are due to the presence of polar or polarizable groups. Aromatic rings and multiple bonds between carbon and nitrogen or oxygen are especially common. Moreover, many liquid crystals are composed of molecules with two similar halves connected by a unit having a multiple bond. Figure 11.27 Structures of Typical Molecules That Form Liquid Crystals*. Answer: spiral structure

A: In the nematic phase, only the long axes of the molecules are parallel, and the ends are staggered at random intervals. in the smectic phase, the long axes of the molecules are parallel, and the molecules are also arranged in planes. finally, in thecholesteric phase, the molecules are arranged in layers; each layer is rotated with respect to the ones above and below it to give it this?
****
Q: Passage: Imagine walking in the forest in Figure below . The towering trees have been growing here for hundreds of years. It may seem as though the forest has been there forever. But no ecosystem is truly static. The numbers and types of species in most ecosystems change to some degree through time. This is called ecological succession. Important cases of ecological succession are primary succession and secondary succession. Answer: ecological succession

A: The numbers and types of species in most ecosystems change to some degree through time and this is called?
****
Q: Passage: In combination or synthesis reactions, two chemical species combine to produce a new compound. The general expression for a combination reaction is:. Answer: new compound

A:
In combination or synthesis reactions, two chemical species combine to produce a what?
****