If We Assume the Traditional View of Existential Import, Why

Multiple Choice

If we assume the traditional view of existential import, why is the following syllogism invalid? All of my uncles have difficult jobs.
All of my uncles are coal miners.
All coal miners have difficult jobs.

A) undistributed middle
B) illicit major term
C) illicit minor term
D) two negative premises
E) negative premise with affirmative conclusion, or negative conclusion with no negative premise