Which of the following solutions is hypotonic with fluids in RBC (Assume that isotonic solid substance completley dissociattes in the solution?

-0.2 M NaCl

-0.1 M NaCL

-0.18M NaCL

-GIVEN ALL

And HOW?

Two solution are said to be isotonic when they have same osmotic pressure. 

For RBC. isotonic solution is 0.9% by (w/V).

Hypertonic solutions are those solution which have concentration above isotonic solution and hypotonic solutions are the solutions having lower concentration than the isotonic solution . 

In terms of molarity, the concentration of isotonic solution for RBC can be determine as follows:

Given 0.9 % solution.

Which means 

0.9 g of NaCl in 100 ml of solution

⇒ 1ml contain → 0.9/100 g of NaCl

⇒ 1000 ml contain  →  9 g of NaCl

Hence, in one liter, 9 g of NaCl is present. 

Number of moles of NaCl in one liter of solution = 9/ 58.5

Hence, the molarity of the solution is 0.15M. 

Therefore, solutions having concentration less than 0.15 M are said to be hypotonic for RBC.

Hence, the correct option is B, i.e., 0.1 M solution.