What properties are indicative of T Tauri stars?

T Tauri stars are in a specific evolutionary stage of stellar development, typically associated with young, variable stars that are in the process of forming. A key characteristic of these stars is their strong stellar winds and prominent emission lines in their spectra.

The presence of strong stellar winds indicates significant mass outflow, which is a common phenomenon for T Tauri stars as they are actively accreting material. Additionally, these stars display a variety of emission lines due to the hot gases around them, which arise from processes such as shock heating and interaction between the stellar winds and surrounding material. These emission lines can often be seen in the hydrogen, calcium, and sodium parts of the spectrum, which are signatures of their dynamic environments.

Together, these properties signal that T Tauri stars are youthful and still undergoing substantial physical changes as they evolve toward the main sequence phase of development. Other options described pertain to characteristics that do not accurately reflect T Tauri stars, making the second choice the most suitable response in this context.