Select the sentence that correctly uses commas in a non-restrictive phrase. a. A river, that is polluted, is unsafe for swimming.
b. Polluted rivers, which can exist anywhere, are unsafe for swimming.
c. When a river becomes polluted, it is no longer safe for swimming.
d. However, rivers sometimes become polluted when nearby farms use too many poisons.

Aturning operation is performed with following conditions: rake angle of 12°, a feed of 0.35 mm/rev, and a depth of cut of 1.1 mm. the work piece is aluminum alloy 6061 with t6 heat treatment (a16061-t6). the resultant chip thickness was measured to be 1.0 mm. estimate the cutting force, fc. use shear stress of 207 mpa and coefficient of friction on the tool face of 0.6.