Sorry, I am going to call myself a careless person for putting the
without checking what you said...

you said
(1.6,8)(16,8)(1 3/5,8)

is equivalent to

(1.6,8)(16,8)(1.6,8) since 1 3/5 is actually 1.6

But it still is a many to one function because a single element in domain is mapped to a unique element in range.

If it is given like ...
(1.6,8)(16,8)(1.6,2)

then 1.6 is mapped to two different values. So it is not a function.

But in (1.6,8)(16,8)(1.6,8)

1.6 is mapped to only one value 8
16 is mapped to only one value 8

So this is a valid many to one function.

This supports my earlier asssumption. I would bet on d.