The intermolecular forces are the strongest in
solids
Correct option (b) -solids
The attractive force among the molecules of a solid is called intermolecular force which is strong in solids.
Incorrect options (a)-liquids -Intermolecular force among liquid is weaker in liquids compare to solids.
(d) Gases-the intermolecular forces in gases are extremely weak that their magnitude is almost zero thus they flow in all directions easily.
Also option (c) is incorrect .