Based on accelerator mass spectrometry, an advanced technique that makes it possible to obtain radiocarbon dates from samples much smaller than that necessary for traditional radiocarbon dating, scholars have been able to determine impressively precise radiocarbon ages for samples of Glyptodon and Holmesina recovered from the La Brea Tar Pits, extinct large mammals similar to armadillos.
a) The sentence is starting with a verb-ed phrase. The noun that verb-ed phrase or word modifies must immediately precede it or follow it. Scholars have been able to determine something using accelerator mass spectrometry.
b) The noun+noun modifier: an advanced technique that makes…………dating modifies mass spectrometry.
c) That refers to advanced technique and thus takes a singular verb. But this is the verb for that and not advanced technique.
d) Scholars is a plural noun and thus take plural verb form ‘have been’.
e) Recovered is again a verb-ed modifier that modifies the preceding nouns Glyptodon and Holmesina.
f) Extinct large mammals similar to armadillos is a dangling modifier. The placement of this modifier is incorrect. Extinct…………..are called noun phrases and technical term for such modifiers is appositive phrases which must be placed close to the noun they modify.
Options:
Based on accelerator mass spectrometry, an advanced technique that makes it possible to obtain radiocarbon dates from samples much smaller than that necessary for traditional radiocarbon dating, scholars have been able to determine impressively precise radiocarbon ages for samples of Glyptodon and Holmesina recovered from the La Brea Tar Pits, extinct large mammals similar to armadillos.
Incorrect
Based on accelerator mass spectrometry, an advanced technique that makes it possible to obtain radiocarbon dates from samples much smaller than necessary for traditional radiocarbon dating, scholars have been able to determine impressively precise radiocarbon ages for samples of Glyptodon and Holmesina, extinct large mammals similar to armadillos, recovered from the La Brea Tar Pits.
Same verb error
Using accelerator mass spectrometry, an advanced technique that makes it possible to obtain radiocarbon dates from samples much smaller than those necessary for traditional radiocarbon dating, scholars have been able to determine impressively precise radiocarbon ages for samples of Glyptodon and Holmesina, extinct large mammals similar to armadillos, recovered from the La Brea Tar Pits.
Correct answer. Using accelerator mass spectrometry, scholars have been able to determine something.
Basing them on accelerator mass spectrometry, which allowed them to obtain radiocarbon dates from samples much smaller than those necessary for traditional radiocarbon dating, scholars have been able to determine impressively precise radiocarbon ages for samples of Glyptodon and Holmesina, extinct large mammals similar to armadillos, recovered from the La Brea Tar Pits.
The pronoun ‘them’ does not have a clear antecedent. And this choice sounds awkward. Basing them on something, scholars did something. Not a very good construction.
The use of accelerator mass spectrometry, an advanced technique that makes it possible to obtain radiocarbon dates from samples much smaller than those necessary for traditional radiocarbon dating, have enabled scholars to determine impressively precise radiocarbon ages for samples of Glyptodon and Holmesina recovered from the La Brea Tar Pits, extinct large mammals similar to armadillos.
The use (singular subject) does not agree with plural verb (have enabled).
Important point to understand:
1) A verb-ed modifier always refers to the CLOSEST noun. For example:
Disappointed by his performance in recent exams, Jake decided to party tonight.
To check if this modifier is correct or not:
Jake is disappointed by his performance in recent exams.
If it makes sense then the placement of modifier is correct.
Therefore in this sentence, verb-ed has been changed to verb-ing.