SC: Fossils of the arm

[RonPurewal]

please restrict your questions to the answer choices given.
thank you.

[AsadA969]

Sure. Thank you.

[RonPurewal]

.

[JWL792]

Ron - is the usage of AND incorrect in A)

Fossils of the arm of a sloth found in Puerto Rico in 1991, and dated at 34 millions year old"

the ", and" make it look like an independent clause but it isn't, should it be just "and " .

I'm having a tough figuring about when to " , and " vs " and ".
Much thanks

that's one way of eliminating that choice, although you have to be VERY careful in making that judgment -- it's quite possible to have a comma in front of "and" in a construction that's not an independent clause, if that comma belongs to some other construction (such as a modifier).

for instance:
i bought bananas and grapes --> normal parallel structure; there shouldn't be a comma here.
i bought bananas, which were on sale, and grapes. --> here there is a comma in front of "and", but that comma belongs to the green modifier.

--

what's probably an easier way to eliminate the same choice is to realize that you can't block off a modifier with a comma on only one side. modifiers should be blocked off either with commas on both sides (nonessential modifiers) or with commas on neither side (essential modifiers).
in that choice, "found in Puerto Rico in 1991" is blocked off with a comma on the right, but not on the left. bad news.

Hi Ron,

Sorry to open this thread again.

For the modifier "found in Puerto Rico in 1991", as you mentioned above, only one comma exists on the right. Maybe we should not use this reason (modifiers only have comma at one side) to eliminate answers? I've found below example in OG2017 -
"First tranches cut into a 500-acre site at Tell Hamoukar, Syria, have yielded strong evidence.....".

Kindly let me know if i'm wrong? thanks a lot.

[Sage Pearce-Higgins]

I'm not sure if Ron's 'comma on one side' rule is really useful for everyone (I've not thought of things in that way when solving problems). However, your example doesn't break the rule, as the commas belong to the appositive modifier "Syria", which is giving information about Tell Hamoukar.