Solve this:
Q. Crystals can be classified into basic crystal habits, equal to
(a) 7
(b) 4
(c) 14
(d) 2

Dear Student,

The crystals are made up of simplified unit cell and these unit cells on the basis of axial length and interfacial angle are classified into 7 crystal system. These crystals systems are as follows: 
1. Cubic Crystal
2. Tetragonal Crystal 
3. Orthorhombic or Rhombic Crystal
4. Monoclinic Crystal 
5. Triclinic Crystal 
6. Hexagonal crystal 
7. Rhombohedral trigonal crystal 

So, the correct option is (a) 

Regards