A pregnancy test is usually reliable. Drugstores have several tests you can buy without a prescription, but a private physician or a county health clinic is the best choice. They can also give the girl a thorough examination and a very reliable pregnancy test. All of this will be completely confidential. A sound, well reasoned, compelling argument is one of the most persuasive communicative acts we humans can create.
Logic is the science of reasoning, proof, thinking, or inference.
Logic allows us to analyze a piece of reasoning and determine whether it is correct or not. To use the technical terms, we determine whether the reasoning is valid or invalid. One does not need to study logic in order to reason correctly. However, a little basic knowledge of logic is often helpful when constructing or analyzing an argument. Note that I am not claiming that logic is universally applicable.