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A heavy steel device that is set on the sea floor and used as a drilling template in offsh
A.temporary guide base
B.permanent guide base
C.guide frame
D.foundation template
![](https://static.youtibao.com/asksite/comm/h5/images/solist_ts.png)
A.temporary guide base
B.permanent guide base
C.guide frame
D.foundation template
A、It has be heavy to prevent astronauts from floating away
B、It must also work as a SCUBA device
C、It needs to double as a hovercraft
D、It must be lightweight and easy to mover in
A.three-fifths
B.three-fives
C.third-fifths
D.three-fifth
According to the text, "nuclear tipped missiles" and "cannonball-size steel spheres" (Para. 5) ______.
A.are different in nature.
B.serve similar functions.
C.are identical to each other.
D.pose real challenges.
To reduce weight, plastic has taken ______ of iron and steel in making boats.
A.its place
B.place
C.the, place
D.a place
A.Coated Carbide
B.High Speed Steel
C.ube-Boronnitride
D.Polymerize Crystal Diamond
A.its place
B.place
C.the place
D.a place
Pistons for modern engines are made of _______.
A cast iron
B steel
C aluminum-alloy
D tin-alloy