How many triangles are there?

As per the given above question figure ,
Mirror image of the given original image will be just opposite to the given line .

As we know that Water image is the reflection of an object into the water . It appears by inverting an object vertically i.e. upside down. The water image always be opposite the original image across the given line. It will become opposite to the given line .
Therefore , required answer will be option D .

On the basis of given figures in above question , we get
In each subsequent figure the three small squares move in anticlockwise direction.
Thus , figure ( 4 ) will come on the place of ? in question figure .As shown in answer figures .

As we know that the mirror image always be opposite the original image across the given mirror. Given image will become opposite to the original image.As shown in given below .

According to given question figure ,
we can say that the mirror image always be opposite the original image across the given line. Given image will become opposite in mirror across the given line MN.As shown in figure .

As we can see that All others have been divided into six parts. But figure (4) is different to others .

As per the given figure in above question, it is clear that
In each subsequent figure the three smaller designs move in clockwise direction along the apex of the triangle and arrow is inverted.
Hence , figure ( 4 ) will come on the place of ? from answer figures .

All outer elements having the replica of its present inside of that, except option (c)