如图所示，在某空间同时存在着相互正交的匀强电场E和匀强磁场B，电场方向竖直向下，有质量分别为m1、m2的a、b两带负电的微粒，a的电荷量为q1，恰能静止于场中空间的c点，b的电荷量为q2，在过c点的竖直平面内做半径为r的匀速圆周运动，在c点a、b相碰并粘在一起后做匀速圆周运动，则（   ）

A．a、b粘在一起后在竖直平面内以速率r做匀速圆周运动

B．a、b粘在一起后仍在竖直平面内做半径为r的匀速圆周运动

C．a、b粘在一起后在竖直平面内做半径大于r的匀速圆周运动

D．a、b粘在一起后在竖直平面内做半径为r的匀速圆周运动

A patrol team of sea lions and dolphins featured in a large-scale military exercises being conducted by the U. S. and its allies in the Pacific Ocean. The machine (1) took part in simulated mine recovery and mine detection missions during the biennial Rim of the Pacific Exercise (RIMPAC) war games. The (2) started on June 19 and will run (3) Friday.
"There are a number of mechanical systems that work in those areas. (4) high-tech gadgets deployed by the military can’t (5) the natural skills of dolphins and lions," said Tom Lapuzza, spokesman for UN Navy’s Marine Mammal Program. Sea lions have "incredible good underwater (6) " and can dive down to 300 meters to catch a recovery line to a mine, he said. Dolphins use sonar to (7) mine.
Human beings have a long (8) of training animals to join the military. Horses have been the most widely-used animals (9) the recorded history of (10) . In early times, horses were used to (11) chariots or to (12) armored forces. With the development of modem weapons and motorized (13) , the use of horses for military purposes fell into (14) . (15) , horses were still used (16) by the German army during World War II for transporting (17) and equipment, including artillery.
During World War II, (18) with explosives strapped to their backs were used as anti-tank weapons. In other (19) , they were used for detecting mines. Some dogs were also used as messengers.
Other animals have also (20) in the military. Recorded history shows the use of elephants for military purposes as early as 1,100 B. C.. They were employed during World War II by both the Japanese army and the (21) .
There are records showing that over 100,000 reindeer were used by Finland to tow sleds during World War II. They carried the (22) to hospitals, brought supplies to the troops and moved heavy anti-tank weapons. It is well documented that oxen have been (23) used in war as improvised beasts of burden. During World War II, spiders were employed by the Allies to spin silk for (24) in cross-hairs on bomb scopes and other optical instruments. People also are finding that Vampire bats’ ability to use echolocation is very interesting as we (25) to learn how it works and it may benefit the army.