in your question, the phrase "explicit premise" means a straightforward, directly-stated idea or concept. if the answer choice is not directly stated in the passage, it is incorrect. the word "explicit" means something that's stated clearly, so keep that in mind while you go through the answer choices. i suggest you go through them one by one and find evidence in the passage to either prove them correct or incorrect.
A. God can save the trees from sawmills. . .look towards the end of the passage. directly quoted: "God has cared for these trees... but he cannot save them from sawmills and fools." this answer choice is incorrect because the author clearly states that god cannot save the trees from sawmills.
B. It is up to the American people to save the trees. . .found in the same sentence as the evidence above: "God has cared for these trees...but he cannot save them from sawmills and fools; this is left to the American people." this is clearly and directly stated in the passage, that the burden of saving the trees falls to the american people. choice B is correct, but you can still disprove the last two.
C. Trees are able to defend themselves. . .at the start of the passage: "They cannot defend themselves or run away." this answer choice is incorrect, because the opposite of it is directly stated in the passage.
D. Planting new trees will restore the forests. . ."And few destroyers of trees ever plant any; nor can planting avail much toward restoring our grand aboriginal giants." the second half of that sentence basically means, "planting new trees can't help the original plant life that was here." this answer choice is also incorrect, because the author plainly states that forests can't be "fixed" by new trees being planted.