Which best describes the nature of photosynthesis?
a. it is an energy-attracting process.
b. it is an energy-building process.
c. it is an energy-releasing process.
d. it is an energy-storing process.

Photosynthesis can be defined as the process by which some organisms and green plants use the sunlight in order to make their food from the water and carbon-dioxide. The photosynthesis is a energy-storing process as it stores the energy of the sunlight in the form of the bonds of the glucose molecules. These bonds are broken when energy is needed by the cells.

Hence, the correct answer is 'Option D - it is an energy-storing process'.

The right answer is A) pili

Pilus (plural pili) is an extension of a protein located on the surface of the wall of many Gram-negative bacteria (and exceptionally Gram-positive bacteria), shorter and finer than flagella, they can not be involved in mobility. They are divided into two categories: the common pili and the sexual pili (which, despite this name, have nothing to do with reproduction, but rather with transmission and its coding).

Cilia is a wrong answer because the point of insertion of eyelashes and flagella is in the cytoplasm, in contact with the plasma membrane. So these are not extensions of the bacterial wall.