Explanation:

Let’s break it down:

- a) “PB Shelly was an English poet.” This introduces the subject. Makes sense to start here.

- d) “Born into a wealthy upper-class family.” Adds background detail about Shelly, fits naturally right after the intro.

- c) “He detested tyranny and institutionalised servitude.” This tells us about his beliefs, best placed after his background is set.

- b) “He was expelled from Oxford for publishing a tract entitled ‘The Necessity of Atheism’.” Now we get a specific event in his life, which logically follows from knowing what kind of person he was.

Let’s look at the options:

Option 1: d, c, a, b—Starts with background before mentioning Shelly. Not ideal.

Option 2: a, d, c, b—Starts with Shelly, then gives background, personality, and event. This flows perfectly.

Option 3: a, b, c, d—Event (expulsion) comes before context; a bit jumbled.

Option 4: c, a, b, d—Starts with beliefs before you even know who he is.

So, option 2 tells a natural story—the person, his upbringing, worldview, then a notable event. That’s the best fit.