'(A) The number of people migrating into Bengaluru has increased significantly in recent years.
(B) This is because Bengaluru provides more economic opportunities than the towns and villages from which these migrants come.
(C) This sudden influx of migrants has made the city less pleasant to live in.
(D) The success of the government's rural employment guarantee act might have the effect of stemming some rural-urban migration.'
Which one of the above statements is best described as an assertion of opinion rather than an assertion of fact?