What line, formally authorized for use where great strength was required, is made from the abaca plant?

Manila line is the correct answer because it is specifically made from the fibers of the abaca plant, which is native to the Philippines. This type of line is known for its exceptional strength, durability, and resistance to salt water, making it particularly well-suited for marine applications where high tensile strength is essential. Manila line is often used in a variety of rigging applications and for anchoring due to its reliability under heavy loads.

Other types of lines, such as jute, cotton, and hemp, are made from different plant materials and do not possess the same characteristics or applications as Manila line. While hemp, for example, is also a strong fiber and has historical significance in maritime use, it is derived from the hemp plant rather than the abaca plant and does not have the same properties that make Manila line particularly useful in environments requiring high strength.