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

[EX Q]: Passage: Red litmus paper turns blue when placed in a basic solution. Answer: blue
[EX A]: Red litmus paper turns what color when placed in a basic solution?

[EX Q]: Passage: The body of a cnidarian consists of two cell layers, ectoderm and endoderm. The cells surround a digestive cavity called the coelenteron (see Figure below ). Cnidarians have a simple digestive system. The single opening is surrounded by tentacles, which are used to capture prey. The tentacles are covered with nematocyst cells. Digestion takes place in the coelenteron. Nutrients are absorbed and gases exchanged through the cells lining this cavity. Fluid in the coelenteron creates a hydrostatic skeleton. Answer: tentacles
[EX A]: Cnidarians have a simple digestive system with a single opening surrounded by what type of structures, which are used to capture prey?

[EX Q]: Passage: The top layer of water farther from shore is called the limnetic zone. There is enough light for photosynthesis and plenty of dissolved oxygen. However, dissolved nutrients tend not to be as plentiful as they are in the littoral zone. Producers here are mainly phytoplankton. A variety of zooplankton and fish also occupy this zone. Answer: limnetic zone
[EX A]:
What is the top layer of water farther from shore called?