Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
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Question: Collision frequency is greater for homogeneous category of catalysts, which also tend to be more sensitive to temperature and more 'expensive'.

Answer: Collision frequency is greater for what category of catalysts, which also tend to be more sensitive to temperature and more 'expensive'?

Question: You call egg-shaped galaxies, which are reddish to yellowish in color because they contain mostly old stars, elliptical galaxies.

Answer: What do you call egg-shaped galaxies, which are reddish to yellowish in color because they contain mostly old stars?

Question: Secondary consumers (which eat primary consumers) are considered to be trophic level 3.

Answer:
What trophic level are secondary consumers (which eat primary consumers) considered to be?