The number 6.022 × 1023 indicating the number of atoms or molecules in a mole of any substance
Answer:

Explanation:
The formula for efficiency is

Data:
Useful energy = 3 J
Energy input = 30 J
Calculation:

I believe the answer is A.
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Answer:
Name, Thallium. Symbol, Tl. Atomic Number, 81. Atomic Mass, 204.3833 atomic mass units. Number of Protons, 81. Number of Neutrons, 123. Number of Electrons, 81 ... It has a metallic luster when it is first exposed to air but it tarnish quickly
Explanation:
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