Bunuel wrote:

Stn wrote:

It might be wrong, but...do we know that O is the center to conclude that OA=OB ?

Edited to make that clear.

In that case:

(1) Tells us the diameter of the circle and thus allows us to calculate a range of measurements of the circle. Area is one of those measurements.

However, we have got no information about the shaded area and are thus unable to answer the question.

Not sufficient.

(2) Due to the fact that the lines inside the circles cut through the diameter we will have two pairs of angles of equal measurement. The angles will add up to 360 degrees. In this case we can calculate the portion of the circle that is shaded. But we do not know how large the circle is.

Not sufficient.

(1)+(2) As we know the area of the circle from (1) and the part/whole-relationship between the shaded area and the circle from (2) we can answer the question.

Answer: C

edit:

Another question about assumptions:

Can we assume that we are dealing with only two lines in this question? Couldn't O connect to 4 lines that do not extend each other?

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