Which of the Following Is Evidence That the Formation Process

Which of the following is evidence that the formation process of our Galaxy may have included collisions with smaller neighbor galaxies?

A) the presence of millions of new stars, recently formed from clouds of gas and dust
B) the existence of supernova remnants, such as the Crab Nebula, in the Galaxy's disk
C) the observation that objects outside the orbit of the Sun are moving around the Galaxy faster than we expected
D) the observation that globular cluster are arranged in a spherical "halo" around the Galaxy
E) the observation of long moving streams of stars that continue to orbit through our Galaxy's halo