The time needed for a radioactive sample to decay to one-half of its original activity is called the

An alcohol thermometer can measure the freezing point of a liquid that freezes at −80 °C.

Explanation:

A thermometer is a device used to measure temperature. A thermometer must contain a thermometric substance. A thermometric substance is any substance having a particular physical property that changes with temperature.

For all liquid-in-glass thermometers, the property that changes with change in temperature is the height of the liquid. There are two kinds of liquid-in-glass thermometers; mercury-in-glass thermometer and alcohol-in-glass thermometer.

Alcohol-in-glass thermometer measures very low temperatures up to as low as -115°C. If it measures such a low temperature, then it can efficiently measure -80°C hence the answer.

Alcohol-in-glass thermometers have a narrower temperature range than mercury-in-glass thermometer. The later is well adapter for the measurement bof higher tempetures up to 357°C.