API gravity of pure water:\nAt standard conditions, the °API gravity value for water is approximately…

Introduction / Context:
API gravity is a petroleum industry measure of how heavy or light a liquid is relative to water. It is defined to indicate that most crudes (lighter than water) have higher API numbers, while heavier liquids have lower values. Knowing the reference point for water helps interpret the scale correctly.

Given Data / Assumptions:

• API gravity definition: °API = (141.5 / SG_60°F) − 131.5.
• Specific gravity of water at 60°F is approximately 1.000.
• Standard conditions (near NTP/60°F) are assumed for the definition.

Concept / Approach:
Substitute the specific gravity of water into the API formula. The calculation yields the benchmark value for water on the API scale, against which lighter or heavier liquids can be compared. Liquids with API > 10 float on water; those with API < 10 sink in water.

Step-by-Step Solution:

Verification / Alternative check:
If SG slightly deviates from unity at different temperatures, API will shift modestly; however, by definition at 60°F, water maps to 10 °API exactly in this formula, anchoring the scale.

Why Other Options Are Wrong:

• 0 or 1 would imply an SG far from 1 in the formula.
• 100 would correspond to an unrealistically low SG by the API relation.

Common Pitfalls:
Confusing API gravity with Baumé degrees or with mass-density units; forgetting the temperature reference (60°F) in the API definition.

Final Answer:
10