According to the law of thermodynamics, energy is never 100% efficient because

The correct answer for the fill in the blank is 1) Second law and 2) Because of the loss of energy in the form of heat or other form.

According to the Kelvin- Planck statement of second law of thermodynamics, it is not possible for a heat engine ( that operates in a cycle) to convert the absorbed heat completely into work.

This indicates that energy is never 100% efficient.

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.

a scenario where a cell may be needed to perform a form of endocytosis is when transporting large molecules. a scenario where a cell may be needed to perform a form of exocytosis is when releasing the large molecule from the cell.