CREATE TABLE table_68827 ("Date" CLOB, "Location" CLOB, "Nature of incident" CLOB, "Circumstances" CLOB, "Casualties" CLOB)

What is the nature of the incident that's a bomb attack?
SELECT "Nature of incident" FROM table_68827 WHERE "Circumstances" = 'bomb attack'
SELECT "Nature of incident" FROM "table_68827" WHERE "Circumstances" = 'bomb attack'