Task: Text to Code
Input (English): Step 1: For each row in airports table, find the corresponding rows in routes table.
Step 2: only keep the results of step 1 whose country equals China.
Step 3: find the number of rows of each value of src_apid in the results of step 2.
Step 4: find country of the results of step 2 with largest value in the results of step 3
Output (English): SELECT T2.country FROM routes AS T1 JOIN airports AS T2 ON T1.dst_apid = T2.apid WHERE T2.country = "China" GROUP BY T1.src_apid ORDER BY Count ( * ) Desc LIMIT 1