(A) People have good reason to care about the welfare of animals. (B) Ever since Enlightenment, their treatment has been seen as a measure of mankind's humanity. (C) It is no coincidence that William Wilberforce and Sir Thomas Fox well Buxton, two leaders of the movement to abolish the slave trade, helped found the Royal Society for the Prevention of Cruelty to Animals in 1820s. (D) An increasing number of people go further: mankind has a duty not to cause pain to animals that have the capacity to suffer
Statement (D) is wrong because it does not convey any meaning. It does not form a coherent paragraph. Statement (B) is wrong because the use of the word "mankind's" is redundant