说明控制测量的原则。

It is possible that the majority of the teenagers accepted the advantages of the iPad. In most cases they were expressing strong opinions about it. But today we already know that another three high-end computer tablets(平板电脑) are going on sale, with the aim of taking a bite out of the iPad's market. For tablet computer fans, iPad may not be the only choice, as the Motorola Xoom, the HP Touchpad and the BlackBerry PlayBook will have been launched (推出)by this summer, according to foreign media reports on Tuesday. Here is Product Information Guide as follows. We would like to listen to your reviews later.   

Apple iPad2 Size: 9.7 inch screen, 8.8mm thick Weight: 601g (Wi-Fi only version) Battery life: 10 hours of heavy use Price: a base price of $499(3,278yuan) Available(可使用的): March 11, 2011 in the US Strength: over 65,000 *apps that are fit for the iPad Weakness: lack of USB port and flash support

 

Motorola Xoom Size: 10.1 inch screen, 13mm thick Weight: 730g Battery life: 8hours of heavy use Price: $800(5,252RMByuan) Available: now Strength: great multi-tasking feature, better cameras than the iPad2     Weakness: limited options（选择权）of apps

 

HP Touchpad Size: 9.7 inch screen, 13mm thick Weight: 740g Battery life: 8hours of heavy use Price: not yet announced Available: summer 2011 Strength: killer software features, including a virtual(虚拟的) keyboard which comes in four sizes Weakness: lack of a rear-mounted（后置式） camera which would allow users to get images and photos

 

BlackBerry PlayBook Size: 7- inch screen, 10mm thick Weight: 400g Battery life: 8hours of heavy use Price: not yet announced Available: Spring 2011 Strength: business-oriented, powerful multitasker, excellent data security（安全） Weakness: Some features require users to have a Black-Berry phone

小题1: Which type is the biggest one?

A．Apple iPad 2

B．Motorola Xoom

C．HP Touchpad

D．BlackBerry PlayBook

小题2:Which is True according to the passage?
A. Apple ipad 2 has excellent data security. 
B. Four types above of Battery life are the same.
C. Most people are satisfied with HP Touchpad.        
小题3: Which one can you buy as a present with only 4000yuan RMB at hand?

A．Apple iPad 2

B．Motorola Xroom

C．None of the four

D．Any of the four