The correct answer is b. The sea calmed, but no boats left shore. Option a is incorrect because there are unnecessary commas between the noun and its verb ("sea, calmed" and "boats, left"). Option c is incorrect because when using a semi colon, the phrases on both sides of it should be able to stand alone. While "the sea calmed" can work by itself, "but no boats, left shore" cannot, thus rendering the semi colon incorrect. Additionally, there is an unnecessary comma between the noun "boats" and the verb "left." Finally, option d is incorrect because there should be a comma before the conjunction "but."