Sentence 4 is the odd one out. While sentences 1, 2, 3, and 5 are centered around Peter Singer’s philosophical argument on animal rights, sentence 4 introduces a historical event (the publication of Singer’s *Animal Liberation* in 1975), which is not directly part of the philosophical argument. Hence, it disrupts the coherence of the paragraph.
Arrange into a paragraph:
1. The streets were wet.
2. We decided to cancel the picnic.
3. Dark clouds covered the sky.
4. Soon, it began to rain heavily.