CREATE TABLE table_name_1 (call_sign VARCHAR2, class VARCHAR2, frequency_mhz VARCHAR2)

Which call sign has a Class of A, and a Frequency MHz of 88.7?
SELECT call_sign FROM table_name_1 WHERE class = "a" AND frequency_mhz = 88.7
SELECT "call_sign" FROM "table_name_1" WHERE "a" = "class" AND "frequency_mhz" = 88.7