Explorer of theExtreme Deep

Oceans cover morethan two-thirds of our planet.Yet,just a small fraction of the underwater worldhas been explored.Now,Scientists at the Woods Hole Oceanographic

Institution(WHOI)inMassachusetts are building an underwater vehicle that will carry explorers asdeep as 6,500 meters (21,325.5 feet).The new machine,known as a manned

submersible orhuman-operated vehicle (HOV),will replace another one named Alvin which has an amazing record of discovery,playinga key role in various important and

famous underseaexpeditions.Alvin has been operating for 40 years but can go down only 4,500meters(14,763.8 feet).It's about time for an upgrade,WHOI researchers say.

Alvin waslaunched in 1964.Since then,Alvin has workedbetween 200 and 250 days a year, says Daniel Fornari,a marine geologist anddirector of the Deep Ocean

ExplorationInstitute at WHOI.During its lifetime,Alvin hascarried some 12,000 people on a total of more than 3,000 dives.A newer,betterversions of Alvinis bound to

reveal even moresurprises about a world that is still full of mysteries,Fornari says.It mightalso make the job of exploration a little easier."We take so much forgranted on

land."Fornarisays."We can walk around and see with our eyes how big things are.We cansee colors,special arrangements."

Size-wise,the newHOV will be similar to Alvin.It'll be about 37 feet long. The setting areainside will be a small sphere,about 8 feet wide,like Alvin.It'll carry a pilotand two

passengers.It willbe just as maneuverable.In most other ways,it will give passengers moreopportunities to enjoy the view,for one thing. Alvin has only three windows,the

new vehicle willhave five,with more overlap so that the passengers and the pilot can see thesame thing.

Alvin can go up anddown at a rate of 30 meters every second,and its maximum speed is 2 knots(about2.3 miles per hour),while the new vehicle will be able to ascend and

descend at 44 metersper second.It'll reach speeds of 3 knots,or 3.5 miles per hour.“…a world that is still full ofmysteries"refers to_______.

A.the earth

B.out space

C.the ocean

D.Mars