CREATE TABLE "tank_locomotives" (
  "class" text,
  "railway_number_s" text,
  "quantity" real,
  "year_s_of_manufacture" text,
  "axle_arrangement_uic" text
);

Question: What is the railway number of t 4 ii class?
SQL: SELECT "railway_number_s" FROM "tank_locomotives" WHERE "class"='t 4 ii';

Question: What year was the b n2t axle arrangement, which has a quantity of 31, manufactured?
SQL: SELECT "year_s_of_manufacture" FROM "tank_locomotives" WHERE "quantity"=31 AND "axle_arrangement_uic"='b n2t';