comma doing vs by doing

[thanghnvn]

Unlike amateur clammers, who usually dig clams by hand during the summer, professional clammers// work year-round, using all-weather instruments such as the hydraulic dredge or a 20-foot-long implement known as a bull rake//

A. work year-round, using all-weather instruments such as the hydraulic dredge or a 20-foot-long implement known as a bull rake

B. work year-round by using all-weather instruments like hydraulic dredge or 20-foot-long implements known as a bull rake

C. working year-round and using all-weather instruments such as a hydraulic dredge or a 20-foot-long implement known as a bull rake

D. working year-round use all-weather instruments like hydraulic dredges or 20-foot-long implements known as a bull rake

E. work year-round using all-weather instruments, for example, a hydraulic dredge or 20-foot-long implements known as a bull rake

what is difference between comma+doing and by+ doing ? pls, help

[RonPurewal]

Please post this question correctly, in a new thread. In particular, please fix the following:

"- Please use an underline (not two slashes) for the underlined part of the problem.
There's a "u" button directly above the text field.

- Please use the first few words of the problem as the title of the thread.

- Please provide the official answer to the question.

"- Please indicate the answer choice(s) about which you are asking.

Thanks.