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.
