分析如下语句的查询结果： SQL> select BEGIN_TIME,END_TIME,UNDOBLKS,MAXQUERYLEN from V$UNDOSTAT; BEGIN_TIME END_TIME UNDOBLKS MAXQUERYLEN ----------------- ----------------- ---------- ----------- 02-01-08:11:35:55 02-01-08:11:41:33 14435 29 02-01-08:11:25:55 02-01-08:11:35:55 120248 296 02-01-08:11:15:55 02-01-08:11:25:55 137497 37 02-01-08:11:05:55 02-01-08:11:15:55 102760 1534 02-01-08:10:55:55 02-01-08:11:05:55 237014 540 02-01-08:10:45:55 02-01-08:10:55:55 156223 1740 02-01-08:10:35:55 02-01-08:10:45:55 145275 420 02-01-08:10:25:55 02-01-08:10:35:55 99074 120 undo表空间的块大小是4KB. 如下哪个是undo表空间的最优大小? A 2GB B 4GB C 1GB D 3GB