• Option (b) 1m is correct.

Given :–

• Ranjini had of ribbon.
• Naina had of ribbon.

To Find :–

• The total length of ribbon.

Solution :–

We have to find the total length of the ribbon.

So,

Total length of the ribbon = Ranjini's ribbon + Naina's ribbon

We have,

• Ranjini ribbon =
• Naina ribbon =

Now,

Now, we taking the least common multiple (L.C.M.) of the denominators.

L.C.M. of 2 and 2 = 2.

So,

Hence,

The total length of the ribbon is 1m.

So, the correct option is (b) 1m.