What Are the Relative Compositions of the Materials from Which

question 79

Multiple Choice

What are the relative compositions of the materials from which stars form?

• A)about 74% hydrogen,about 24% helium,no more than 2% other materials
• B)about 24% hydrogen,about 74% helium,no more than 2% other materials
• C)about 2% hydrogen,about 74% helium,no more than 24% other materials
• D)Stars have vastly differing combinations of materials.

Identify correct refrigerant management practices including recovery, recycling, and retrofitting.

Know the properties and uses of various compressor types in truck A/C systems.

Understand the significance of A/C system maintenance, including leak detection and component replacement.

Understand the types of fuel used in truck supplemental coolant heaters.

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Definitions:

Mean

The arithmetic average of a set of numbers, calculated by summing them and dividing by the number of numbers.

Area

A quantity expressing the two-dimensional size or extent of a shape or surface, typically measured in square units.

Variance

A measure of dispersion in a set of data points, calculated by taking the average of the squared differences from the mean.

Standard Deviation

A statistic that quantifies the dispersion or variability of a dataset, measuring the average distance between each data point and the mean.