如图所示，一只上口小、下底大的平底容器装满纯净水放在水平桌面上，容器质量为m，水的质量为M．用F₁表示水对容器底面的压力，P₁表示水对容器底面的压强，F₂表示容器对桌面的压力，P₂表示容器对桌面的压强．则（　　）

A．F₁=Mg

B．F₂=（M+m）g

C．P₁有可能等于P₂

D．P₁不可能等于P₂

What’s your earliest childhood memory Can you remember learning to walk Or talk The first time you heard thunder or watched a television program Adults seldom (1) events much earlier than the year or so before entering school, (2) children younger than three or four (3) retain any specific, personal experiences.

A variety of explanations have been (4) by psychologists for this "childhood amnesia". One argues that the hippo-campus, the region of the brain which is (5) for forming memories, does not mature until about the age of two. But the most popular theory (6) that, since adults don’t think like children, they cannot (7) childhood memories. Adults think in words, and their life memories are like stories or (8) one event follows (9) as in a novel or film. But when they search through their mental (10) for early childhood memories to add to this verbal life story, they don’t find any that fit the (11) It’s like trying to find a Chinese word in an English dictionary.

Now psychologist Annette Simms of the New York State University offers a new (12) for childhood amnesia. She argues that there simply aren’t any early childhood memories to (13) . According to Dr. Simms, children need to learn to use someone else’s spoken description of their personal (14) in order to turn their own short-term, quickly forgotten (15) of them into long term memories. In other (16) , children have to talk about their experiences and hear others talk about (17) — Mother talking about the afternoon (18) looking for seashells at the beach or Dad asking them about their day at Ocean Park. Without this (19) reinforcement, says Dr. Simms, children cannot form (20) memories of their personal experiences.

8（）

A.narratives

B.forecasts

C.communications

D.descriptions