Rarely deeper than 25 feet and broader than 18 feet, but it extended 20 km around the green hills of Greensville, United States, the regional canal connected the Tomes River at Bucon to the Great Plains at Los Gatos, offering an exciting picnic spot to the central community of the local town.
(A)
Rarely deeper than 25 feet and broader than 18 feet, but it extended 20 km around the green hills of Greensville, United States, the regional canal connected
Incorrect. Parallelism: [adjective phrase] and [adjective phrase] but [clause]
(B)
Rarely deeper than 25 feet and broader than 18 feet but extending 20 km around the green hills of Greensville, United States, the regional canal connected
Correct. [adjective phrase] and [adjective phrase] but [adjective phrase], [appositive], the regional...
(C)
It was rarely deeper than 25 feet and broader than 18 feet, and extended 20 km around the green hills of Greensville, United States, but the regional canal, connecting
Incorrect. Missing antecedent of "it"
(D)
The regional canal was rarely deeper than 25 feet or broader than 18 feet and it extended 20 km around the green hills of Greensville, United States, which connected
Incorrect. Meaning changed: "or" instead of "and" and which referring to "Greensville" instead of "the regional canal".
(E)
The regional canal, rarely deeper than 25 feet and broader than 18 feet, but extending 20 km around the green hills of Greensville, United States, connecting
Incorrect. No main verb!