The correct answer is: D. Great oaks are felled by little strokes.
The sentence “Little strokes fell great oaks” is an idiom that means that even small actions can have a big impact over time. In other words, if you keep chipping away at something, eventually you will succeed.
Option A, “Great oaks fell with little strokes,” is incorrect because it implies that the oaks fell on their own, without any outside force. Option B, “Great oaks were felled by little strokes,” is also incorrect because it implies that the oaks were felled by someone or something else, rather than by the little strokes themselves. Option C, “Great oaks can be felled with little strokes,” is incorrect because it implies that it is possible to fell an oak with a single little stroke. However, in reality, it would take many little strokes to fell an oak.
Option D, “Great oaks are felled by little strokes,” is the correct answer because it accurately reflects the meaning of the idiom. The sentence implies that even small actions can have a big impact over time, and that if you keep chipping away at something, eventually you will succeed.