Which of the following constitutes the primary structure of a protein?
a. the folding of a polypeptide chain
b. the linear sequence of amino acids in a polypeptide chair
c. the polypeptide chains stacked on top of each other
d. a pleated sheet
e. several polypeptide subunits

B. The linear sequence of amino acids in a polypeptide chain.

Explanation: Protein structure is the  three dimensional arrangement of amino acid molecules in polypeptide chain.  

Protein has four types of structure -

1-Primary structure

2-secondary structure

3- Tertiary structure

4- Quaternary structure

Primary structure of protein is the simplest form of protein where amino acids are arranged in linear way. One end of polypeptide chain is Called C-terminal (Carboxyl group )and other is called N terminal (amino group). Peptide bods play important role in establishing primary structure of protein.

carbon

explanation:

c. earths continental crust is thicker than its lithosphere.

because, the lithosphere is the outermost layer of the earth/ 100 km thick and is defined by its machanical properties.the lithosphere contains oceanic and continental crust that varies in age and thickness across locations and geologic time. the lithosphere is the coolest layer of the earth in terms of temperature. the term lithosphere should not be confused with the use of "geosphere" which is used to indicate all of earth systems, including the atmosphere, hydrosphere   and biosphere. the surface of the earth can be divided into the continental crust and the oceanic crust.   the continental crust is made mostly of granite while the oceanic crust is made of basalt. the average thickness of the continental crust is 25 miles and the average thickness of the oceanic crust is 5 miles.   three types of rock, igneous, sedimentary, and metamorphic, make up the surface of the earth. that's why 3 option is preferable.