$3.$ For the parallel reaction, A$->$B and A$->$C$,$ if B is the desired product and the reaction A$->$B is of positive order n$1$ and C is the undesired product and the reaction A$->$C is of negative order n$2,$ then increasing the concentration of A $\_\_\_\_\_$

a$)$ Decreases desired product selectivity

b$)$ Increases desired product selectivity

c$)$ Initially increases and then decreases desired product selectivity

d$)$ Does not affect desired product selectivity