(1-1)          Here’s how the interference works out:

If we take the lines to indicate wave peaks, then the points where the semicircular diffracted wave peaks intersect are examples of points where there is constructive interference.  In fact constructive interference is maintained all the way along the lines from the midpoint of the slits to points A and C. This means, in effect that a wave with enhanced amplitude propagates along these lines and hence a bright line will appear on the screen at these points.

On the other hand, you can see that there is no constructive interference along the line to point B. In fact the waves are exactly out of phase along this line, leading to destructive interference and therefore cancellation of the waves’ amplitude:  the screen will therefore remain dark at position B.

These are just examples of these alignments: there will in fact be an alternation of bright and dark fringes on the screen.