Changes are shown in boldface type.
Seventeen articles (the) are missing from the original paragraph.
1 \S > The s\undial is probably \+the\ most ancient of scientific instruments. 2 This instrument tells time by measuring \+the\ passage of \+the\ sun through \+the\ sky. 3 Ancient men measured time by placing a stick in \+the\ ground and by watching \+the\ movement of its shadow. 4 \+The\ Egyptians and \+the\ Greeks constructed \+the\ first sundials, which divided each day into equal intervals called hours. 5 By A.D. 150, Greek mathematicians used trigonometry to plot hour lines. 6 Sundials were used from \+the\ sixteenth to \+the\ nineteenth centuries as \+the\ primary way of telling time. 7 Because sundial time (or solar time) is not \+the\ same as clock time, \+the\ development of mechanical clock and \+the\ adoption of standard time in nineteenth century caused \+the\ sundial to lose its practical value. 8 Nonetheless, sundials are sometimes still used today.
Notes:
Ten articles (a or the) are missing from the original paragraph.
1 Diamonds, \+the\ most precious of all gems, and graphite, \+the\ mineral that is used in pencils, are both composed of \+the\ element carbon. 2 What makes diamonds different from graphite is \+the\ way that its carbon atoms are bonded together. 3 In \+a\ diamond, each carbon atom is bonded with four neighboring carbon atoms under extreme heat and pressure. 4 \+The\ octahedron crystal that is formed is \+the\ hardest known mineral. 5 Diamonds have been valued for centuries because of their rarity and their exceptional hardness. 6 Because only about 20 percent of all diamonds mined are suitable for cutting into gemstones, \+the\ rest are used for industrial purposes. 7 Today, diamonds have become \+the\ most important industrial abrasive, and they are almost indispensable as a grinding material in \+a\ wide range of industrial applications.
Notes:
[Ex 9AB] [Go to class at cvc.blackboard.com] [marsha_chan@wvmccd.cc.ca.us]
Marsha Chan
English as a Second Language Department
Mission College
3000 Mission College Blvd.
Santa Clara, CA 95054-1897
(408) 855-5314
URL: http://www.missioncollege.org/depts/esl/