Gravitational waves were first detected directly in 2015. According to models, the source of these gravitational waves was . A. a neutron star supernova
B. the merger of two black holes
C. the supernova of an extremely massive star
D. a white dwarf supernova
E. very powerful x-ray bursts

Iassume the answer is 75 feet. inwards to outwards rather than outwards to inwards. probably be 75.hachures are stokes drawn in direction of the steepest slope. a series of short parallel lines drawn on a map to indicate topographic relief. it is actually called hachures on contour lines. the small marks in the center of the feature are called hachures.observe the picture attached