Steve Jobs，Apple's chief executive，made his first public appearance since going on medical leave six weeks ago，taking the stage at a San Francisco media event to introduce the iPad 2, the second generation of the company's tablet computer.
Thin but energetic, Mr Jobs showed off a thinner iPad.“We've been working on this product for a while and I just didn't want to miss this day，” he said.
His absence has concerned investors, especially since the group has given no details of his condition.He was diagnosed (确诊) with cancer in 2004 and had a liver transplant (肝脏移植) during almost six months of medical leave in 2009. People close to him said last month his health had been changing.
Apple's stock (股票) rose more than 2 per cent in the minutes after Mr Jobs began speaking, then gave up some of its gain as he detailed the iPad 2.
The iPad 2 will go on sale in black and white versions in the US on March 11 and in 26 other countries, including the UK and Germany, on March 25.
Most of the improvements in the latest version had been expected，including a camera in the front and back for video conferencing，taking photos and videos.The iPad 2 is onethird thinner than the original tablet and slightly lighter.In the US it will work with AT&T and Verizon，the top two mobile carriers(运营商)．The pricing will be the same to the 2010 iPad at its introduction，ranging from $499 to $829 in six models.But Apple dropped prices on the older iPad on Wednesday by $100 across the board.
Apple has made the most of its yearlong head start in tablets, selling 15,000,000 units of the older iPad last year and taking about 85 per cent of the market.It is predicted that the iPad 2 would claim 80 per cent of the US market this year, or 20,000,000 out of 24,000,000 total shipped (出货量)．
Motorola, BlackBerry maker Research in Motion, Samsung and others have brought out competing tablets, many based on Google's Android software.
Mr Jobs said the rest of the field was still catching up with the first iPad and their markets for applications designed for tablets had, at best, 100 small programs.This compares with 65,000 on Apple's applications store.
67．Why are the investors of Apple worried according to the text?
A．Apple's stock price changes a lot.
B．Steve Jobs' health condition is not stable.
C．The iPad 2 has some technical drawbacks.
D．Apple faces strong competition from other companies.
68．In what respect are the iPad 2 and the 2010 iPad exactly alike?
A．The weight.
B．The camera.
C．The thickness.
D．The pricing at the introduction.
69．How many tablet computers were sold in the market last year?
A．About 15,000,000. B．About 17,000,000.
C．About 20,000,000. D．About 24,000,000.
70．What makes Apple's tablets superior to the competing tablets of other companies?
A．The low price.
B．The Android software.
C．The full kinds of models.
D．The tens of thousands of applications.