All the … were stolen by the thieves

Analyze the question: This tests noun number (singular vs plural) and uncountable nouns. We need the correct forms of "arm(s)" and "ammunition" in the phrase "arms and ammunition".

Explain the concept:

• Arms (meaning weapons) is almost always plural. "Arm" in the singular refers to the body part, so "arm and ammunition" would not make sense for weapons.
• Ammunition is an uncountable (mass) noun, like "furniture" or "equipment". It has no plural form, so "ammunitions" is incorrect in standard usage.
• "Arms and ammunition" is also a fixed phrase in standard English.

Step-by-step solution:

1. The sentence says "All the __ were stolen", so the plural verb "were" fits "arms" as a plural noun.
2. Option A: "arm" is singular and wrong here, so it is out.
3. Option C: "arm" is singular and "ammunitions" is wrong, so it is out.
4. Option D: "arms" is correct, but "ammunitions" is wrong because ammunition is uncountable, so it is out.
5. Option B: "arms and ammunition" has the plural "arms" for weapons and the uncountable "ammunition". This is correct.

Correct sentence: "All the arms and ammunition were stolen by the thieves."

Tip: Remember that "arms" (weapons) is always plural, while "ammunition" never takes an "s". Other uncountable nouns that are often wrongly pluralized in exams include equipment, furniture, information, advice, luggage, and machinery.