To which segment belongs the customer that made the most orders in April 1994?
segment refers to c_mktsegment; customer made the most orders in April 1994 refers to c_custkey where o_orderdate LIKE '1994-04-%' and MAX(COUNT(o_orderkey));
SELECT T.c_mktsegment FROM ( SELECT T2.c_mktsegment, COUNT(T1.o_orderkey) AS num FROM orders AS T1 INNER JOIN customer AS T2 ON T1.o_custkey = T2.c_custkey WHERE T1.o_orderdate LIKE '1994-04-%' GROUP BY T1.o_custkey ) AS T ORDER BY T.num DESC LIMIT 1