Just a warning... Stay clear of non-official questions so you don't pick up bad habits. There are a lot of holes in this question and any of these can be answers based on the weighting of the stocks in the portfolio.

Let us assume the price of that has increased by 15% was $x and price of the stock that has decreased by 35% was $y.

As the total price increased by approximately 2%, the increase in price is 2% of (20 + 35 + 40 + 45 + 70) = 2% of 210 = 4.2

So, 15% of x - 35% of y ≈ 4.2
--> 0.15x - 0.35y ≈ 4.2

Clearly, x must be greater than y.
Let us check two extreme values of x and y, i.e. x = 75 and y = 20

(0.15)*70 - (0.35)*20 = 10.50 - 7.00 = 3.50
Note that, this difference cannot be more than this.
So, the closes we can get to $4.2 increase only if prices of $20 and @70 stocks has changed.

Answer : E