Official Solution:Wilhelm I was recognized by the Treaty of Frankfurt as the Emperor in 1871, when Germany first became a single, unified state.A. Wilhelm I was recognized by the Treaty of Frankfurt as the Emperor in 1871, when Germany first became a single, unified state.
B. Wilhelm I was recognized by the Treaty of Frankfurt in 1871 as Emperor, when Germany first became a single, unified state.
C. Germany first became a single, unified state in 1871, when the Emperor Wilhelm I was recognized by the Treaty of Frankfurt.
D. Germany first became a single, unified state in 1871, when the Treaty of Frankfurt recognized Wilhelm I as the Emperor.
E. In 1871, Germany first became a single, unified state, when the Treaty of Frankfurt recognized Wilhelm I as the Emperor of the country.
(A) This sentence illogically implies that the treaty recognized Wilhelm as the Emperor in 1871, when it simply recognized him as the Emperor
(B) The dependent clause beginning with 'when Germany' illogically refers to Emperor
(C) The passive voice construction 'when the Emperor Wilhelm I was recognized by the Treaty' is less idiomatic than the active voice construction of choice D; the word 'the' in 'the Emperor Wilhelm I' is unnecessarily wordy
(D) Correct. The active voice construction 'the Treaty of Frankfurt recognized Wilhelm I' is idiomatically correct
(E) The phrase 'The Emperor of the country' is unnecessarily wordy
Answer: D