单选题

已知表tbl中字段land_ID建有索引，字段cust_id建有唯一索引，下列语句查询逻辑相同，其中执行效率最优的是

Question

A. SELECT * FROM tbl WHERE land_id > 750 or (cust_id=180 or cust_id=560)

B. SELECT * FROM tbl  WHERE (cust_id=180 or cust_id=560) or land_id > 750

C. SELECT * FROM tbl WHERE land_id > 750 UNION SELECT * FROM tbl WHERE cust_id = 180 UNION SELECT * FROM tbl WHERE cust_id = 560

D. SELECT * FROM tbl WHERE land_id > 750 UNION ( SELECT * FROM tbl WHERE cust_id = 180 UNION ALL SELECT * FROM tbl WHERE cust_id = 560 )