旋涡泵与离心泵在相同的叶轮直径和转速下旋涡泵的扬程比离心泵高（）倍。

Dogs are constantly learning from the reaction of human owners, picking up facial cues and anticipating their owner’s behavior, a new research suggests. The findings, published online in the journal Learning and Behavior, show that dogs essentially are always in training, and help explain how many owners unknowingly teach and reward their dog’s bad behavior.

Research conducted at the University of Florida focused on the role of eye contact and facial cues in influencing canine behavior. Earlier studies have suggested that dogs seem to know when they are being watched and even wait to perform forbidden behavior like digging in the garden when they know their owners aren’t looking. In this study, researchers studied how human cues triggered begging behavior among 35 pet dogs, 18 shelter dogs and 8 wolves raised in captivity. First the animals were taught that the human strangers helping with the experiment were reliable sources of tasty treats. The testers stood close together and called to the animal, and both offered rewards of Spam cubes or Beggin’ Strips treats.

After four rewards, the experiment began. Two testers stood against a fence or wall, about 20 feet apart and with food in their pockets. The dog was held about 20 feet away, equidistant from both testers. In one condition, one tester faced the dog while the other turned her back. In another, a tester held a book near her face, while the other tester held the book in front of her face, as if she were reading. In a third condition, one tester held a bucket near the shoulder, while the other put the bucket over her head, blocking her eyes.

Then, both testers called out to the dogs. All the animals—pet dogs, shelter dogs and wolves—ignored the person whose back was turned and sought food from the person who was looking at them. "The question was, are dogs and wolves responsive to a human’s attentional state" said Monique Udell, an assistant professor of psychology at Flagler College, Fla. But when the testers held books, it was only the domestic dogs who avoided the person who appeared to be reading the book. "In a house where they’re used to people reading books, they are sensitive to those types of cues," said Dr. Udell. Interestingly, in the bucket experiment, the animals, for the most part, were equally likely to seek food from the person with the bucket over her head as the person holding the bucket.

The experiment shows that dogs are tuned into whether humans are paying attention. "Dogs don’t have to read our minds. Dogs read our behavior," said Dr. Udell. Pet owners often get frustrated with bad dog behavior without realizing that they themselves have reinforced it, either by giving the dog a treat when they beg, skipping a bath when they protest or letting them sleep on the bed or couch.

The possible reason why most animals turned to the person with the bucket is that（）

A. they thought the bucket contained food

B. they could not read that cue

C. the person did not turn his back on them

D. the person only half hid his face

下列哪项不是急性上呼吸道感染的部位()

A.气管

B.鼻

C.咽

D.喉

E.鼻窦

引起细菌性食物中毒的中毒食品主要是（）

A.乳类及其制品

B.海产品

C.豆类及其制品

D.剩米饭、米粉

E.畜肉类及其制品

库存的作用主要是能有效地缓解供需矛盾，尽可能均匀地保持生产。

在如图1-11所示的树形文件系统中，方框表示目录，圆圈表示文件，"/"表示路径中的分隔符，"/"在路径之首时表示根目录。假设当前目录是D2，进程A以如下两种方式打开文件f2：方式①fd1=open（"（1）/f2"，ORDONLY）；方式②fd1=open（"/D2W2/f2"，O_RDONLY）；其中，方式①的工作效率比方式②的工作效率高，因为采用方式①，文件系统是从（2）。

空白（2）处应选择（）

A.根目录开始查找文件f2，系统查找时间少，读取f2文件次数不变

B.当前路径开始查找文件f2，系统查找时间少，读取f2文件次数少

C.根目录开始查找文件f2，系统查找时间少，读取f2文件次数少

D.当前路径开始查找文件f2，系统查找时间少，读取f2文件次数不变