Answer: d. The temperature of the liquid is 60°C.
Step-by-step explanation:
A quantitative observation is an observation of measure of variables sing in the study or experiment . Variables can be length, weight, temperature , volume etc which can be measured.
From all the given options only option d. is describing a measure ( 60°C).
Hence, an example of a quantitative observation: "The temperature of the liquid is 60°C."
So correct option is d.