Define fundamental unit ? write its two example. ​

the International System of Units, the fundamental units are: The meter (symbol: m), used to measure length. The kilogram (symbol: kg), used to measure mass. The second (symbol: s), used to measure time. The ampere (symbol: A), used to measure electric current.

in this image, you can see solar radiation going through ocean water.

no image, but probably absorption

the answer is b, have negligible mass