The smallest number of straight lines that will divide a plane into 5 regions isA. 3B. 4C. 5D. 6E. 2010

The answer is B. 4.

Here's the step-by-step explanation:

1. Draw the first line. This divides the plane into 2 regions.
2. Draw the second line. If you draw it intersecting the first line, it will divide the plane into 4 regions.
3. Draw the third line. If you draw it intersecting the first two lines, it will divide the plane into 6 regions. But we only need 5 regions.
4. So, we draw the third line in such a way that it intersects only one of the existing lines. This will divide the plane into 5 regions.

Therefore, the smallest number of straight lines that will divide a plane into 5 regions is 4.