With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Cancer did not cause deaths.
text_B: N1000 series may refer to the following  :. Keikyu N1000 series. Keikyu N1000 series. Keikyu N1000 series. Nagoya Municipal Subway N1000 series. Nagoya Municipal Subway N1000 series. Nagoya Municipal Subway N1000 series
not_related.