IMO : C. Together its sufficient to answer the question.

OA is E

guys!...some explanations pls!!

(1)
Leslie traded 5 times and Kerri traded 20 times.
But there is no info about total investment or successive returns.
Not sufficient

(2)
We get a ratio of their individual investments, but no info about successive returns to compare.
Not sufficient

combining,
successive returns are still not available.

Thus E

This is just a wild guess. I am looking forward to the exact explanation.

Statement 1) Without information about the starting amounts, we cannot determine who made more money. Leslie could have started with $1,000,000 and Kerri with $1, or Leslie with $1 and Kerri with $1,000,000. These scenarios give different results in terms of the question stem. Insufficient.

Statement 2) Without information on the percentage return, the beginning amounts don't help us determine who made more money. Leslie could have a 1,000,000% return and Kerri a 1% return, or vice versa. Insufficient.

Combined) The key to this problem is that it deals with the two-year arithmetic average return. Think about what this means:

Let's take Kerri as an example. She has a 5% average return over the two years. It is possible that she had a 5% return both years, or that she had a 110% return one year, and a -100% return the following year. A negative 100% return would leave her with $0 at the end of year 2. The fact that we don't know the yearly returns makes the combined statements insufficient.

Another example of how these problems need to be read and interpreted very carefully!

goalevan wrote:
Combined) The key to this problem is that it deals with the two-year arithmetic average return. Think about what this means:

Let's take Kerri as an example. She has a 5% average return over the two years. It is possible that she had a 5% return both years, or that she had a 110% return one year, and a -100% return the following year. A negative 100% return would leave her with $0 at the end of year 2. The fact that we don't know the yearly returns makes the combined statements insufficient.

Another example of how these problems need to be read and interpreted very carefully!

That's a good observation and the right answer, E!