Question

in 1930, physicist subrahmanyan chandrasekhar began developing a mathematical model predicting that stars above a certain mass would collapse into dense remnants. his theory was initially dismissed by senior astronomers who believed that all stars would eventually become white ___ later, the model—now known as the chandrasekhar limit—was validated and set at approximately 1.4 solar masses, forming the basis for understanding neutron stars and black holes.
18
which choice completes the text so that it conforms to the conventions of standard english?
a dwarfs, however, decades
b dwarfs, however. decades
c dwarfs, nevertheless, decades
d dwarfs: nevertheless, decades

Explanation:

To solve this, we analyze punctuation and capitalization:

1. The first part ("His theory was initially dismissed... white dwarfs") and the second part ("later, the model...") show a contrast. "however" and "nevertheless" are conjunctive adverbs. For punctuation, after a conjunctive adverb used to join two independent clauses, we need a semicolon or a period before it (or a comma if it's in the middle, but here it's between two clauses). But looking at the options, we also need to check capitalization of "decades".
2. Option A: "however" after a comma is incorrect for joining two independent clauses (should be a semicolon or period before "however").
3. Option B: "however" is preceded by a period (correctly separating the two independent clauses), and "Decades" is capitalized (since it starts a new sentence after the period), which fits.
4. Option C: "nevertheless" after a comma is incorrect for joining two independent clauses (needs a semicolon or period before).
5. Option D: The colon before "nevertheless" is incorrect as a colon is for explanation or list, not contrast between clauses. Also, "nevertheless" here would need proper punctuation before.

Answer:

B. dwarfs, however. Decades