Some bacteria are metabolically active in hot springs because A) ...

[Hawke]

Some bacteria are metabolically active in hot springs because
A) they are able to maintain a lower internal temperature.
B) high temperatures make catalysis unnecessary.
C) their enzymes have high optimal temperatures.
D) their enzymes are completely insensitive to temperature.
E) they use molecules other than proteins or RNAs as their main catalysts.

[Sandstorm]

Try C. I remember this question on my exam.