The correct answer is option 'B' - sp2 and sp.

Explanation:
In allene (C3H4), there are two carbon atoms, each with three sigma bonds. To determine the hybridization of the carbon atoms, we need to look at their bonding and lone pairs of electrons.

1. Hybridization of the first carbon atom:
- The first carbon atom is bonded to two other carbon atoms and one hydrogen atom.
- It has three sigma bonds, which means it will have three hybrid orbitals.
- The carbon atom also has one lone pair of electrons.
- The presence of three sigma bonds and one lone pair indicates sp2 hybridization.
- Therefore, the first carbon atom is sp2 hybridized.

2. Hybridization of the second carbon atom:
- The second carbon atom is also bonded to two other carbon atoms and one hydrogen atom.
- It also has three sigma bonds, which means it will have three hybrid orbitals.
- The carbon atom does not have any lone pairs of electrons.
- The presence of only three sigma bonds indicates sp hybridization.
- Therefore, the second carbon atom is sp hybridized.

In summary, in allene (C3H4), the type of hybridization of the carbon atoms is sp2 and sp.