Which structures represent 2-methylbutane? check all that apply?

2-methyl butane is an organic compound with a molecular formula of C5H12,

Isomers are compound with the same molecular formula but different structural formula. Therefore 2-methyl butane may exhibit isomerism and may be represented in different structural formulas but maintaining the same molecular formula. I believe that the structures that represent 2-methyl butane will be

a, b, c, and d.