Respuesta :

Answer:

Spheroidite   <  Pearlite   <  Bainite   <  Martensite

Explanation:

Given materials in the question :

Pearlite, martensite, bainite and spheroidite

Now,

the correct order of the increasing toughness out of  the given materials is

Spheroidite   <  Pearlite   <  Bainite   <  Martensite

These all are the forms of steel formed by different heating and cooling processes.