Precision can be defined as the
exact center of a data set.
reproducibility of a measured value.
correlation between two variables that are measured in a data set.
agreement between a measured value and an accepted value.

Precision can be defined as the 
reproducibility of a measured value.

Precision is how close the measured values are to each others. In contrast with accuracy, accuracy is the agreement between a measured value and an accepted value. Accurate data are always precise while precise data is not always accurate.

The answer is b on plato.

The answer is a) carbon-12