Which word is most opposite in meaning to tenacious?

Correct my question my english is not good: “what the effect and the effectiveness of strength exercise in breast cancer medication related to lymphedema? ”

What is the problem with the following sentence: cameron, who has an extreme and unreasonable suspicion of other people and their motives, suffers from paranoia which is a psychological disorder characterized by delusions of persecution or grandeur, was absolutely sure that someone was following him even though he was absolutely alone and hadn't seen a car for miles and miles.

Biologists recognize five levels of cell organization. the lowest and simplest is the cellular level. organisms here are either unicellular organisms, like protozoa, or colonial organisms. colonial organisms are composed of single-celled individuals that stay together to sustain the life of the whole colony. next on the scale of complexity is the level occupied by tissue. a tissue is a group of similar cells which perform a similar activity. tissues that are organized around a common function together make up an organ, the third level of complexity. the fourth level of organization is the system, formed by a group of organs which together perform a specific bodily process. the fifth and highest level is the organism level, in which body systems work together in a structure capable of independent life. main idea: