If the number of elements in Co-domain is greater than number of elements of domain, then the function cannot be onto...
If the number of elements in domain is greater than codomain,then the function cannot be one-to-one.
Here number of elements in co-domain is greater than domain,so obviously there will be atleast one element in co-domain which will not have a preimage in the domain. But it can be one-to-one...
So Option B)