The basic unit for mass is the
a. gram.
c. cubic meter.
b. metric ton.
d. meter.

The correct answer is option a.

Explanation:

Basic unit to measure mass is defined as the unit which is commonly used to measure the mass of an object.

From the given options,

Option a: Grams is a unit which is used to measure mass and it is the commonly used unit.

Option b: Cubic meter is the unit which is used to measure the volume of an object.

Option c: Metric ton is a unit which is used to measure the mass of an object but this unit is not commonly used. hence, this is not  basic unit to measure mass.

Option d: Meter is the unit which is used to measure length.

From the above information, the correct answer is option a.

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.