Admiralty brass used for steam condenser tubes contains copper and zinc in the following ratio

Answer: Option C

The correct answer is Option C: 70 : 30.
Let's break down why:
Admiralty brass is a specific type of brass alloy.
Brass is primarily made of copper and zinc.
Admiralty brass has a typical composition of approximately 70% copper and 30% zinc, and also contains a small amount of tin (around 1%) to improve corrosion resistance, especially in seawater applications like steam condensers.
Therefore, the ratio of copper to zinc in admiralty brass is closest to 70:30.
The other options are incorrect because they do not reflect the standard composition of admiralty brass.