Answer:
D. organ systems
Explanation:
Organs and tissues that perform the same function are called organ systems
An internal skeleton is used to help an organism hold its body up and keep from falling, while a stem stores nutrients, and produces new living tissue, and transports fluids.
The time period being referred to is the sensitive period. This time period is also referred to as the critical period. The importance of a critical period is such that it must involve certain stimuli from which an organisms learns and acquires traits. If some of these stimuli are not present in the critical period, the organism has difficulty acquiring the trait or skill, and may even find it to be impossible to learn the skill.
Vascular tissue<span> is a complex conducting </span>tissue<span>, formed of more than one cell type, found in </span>vascular plants<span>. The primary components of </span>vascular tissue<span> are the xylem and phloem.</span>
