How did the “infrared thermometer” come about?

Explanation:

NASA - created it

1899 - invented

The earliest infrared thermometer (IRT) was known as the disappearing-filament optical pyrometer. 1899, The first patent for disappearing-filament optical pyrometer: The first patent for the optical pryometer was granted to Morse in 1899.

NASA

Explanation:

An infrared thermometer is a thermometer which infers temperature from a portion of the thermal radiation sometimes called black-body radiation emitted by the object being measured. ... Infrared thermometers are a subset of devices known as "thermal radiation thermometers".

a. because the u.s. was the leading with the most technology, economy, etc. also was teamed with other allies witch boosted the economy and materials to improve technology and use it.

your answer would be (b)