The outermost tissue of a tree trunk that is 6 feet in diameter would most likely be cork. This is because in woody plants, the epidermis is replaced by a thicker, protective layer known as the periderm as the plant matures. The periderm includes the cork cambium, cork cells, and phelloderm. The cork cells contain a waxy substance called suberin that repels water and protects the plant against physical damage, as well as reducing water loss. Since the question references a tree trunk, which is a mature structure, the correct choice is (B) cork.
The outermost tissue of a 6-foot diameter tree trunk is cork. This cork is part of the periderm, which includes the cork cambium, and provides protective functions for the tree. Therefore, the correct answer is (B) cork.
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