The Text Attributes the Catastrophic French Defeat in the Spring

The text attributes the catastrophic French defeat in the spring and summer of 1940 to

A) poor French generalship.
B) French and British material inferiority.
C) the sudden surrender of the Belgians, which opened huge gaps in the French line.
D) the work of Fascist fifth-columnists inside France.
E) British failure to aid the French.