A radioactive element is an element which is subject to spontaneous degeneration of its nucleus followed by the emission of alpha, beta and gamma particles. All elements with atomic numbers greater than 83 are radioactive.
The given phrases that describe radioactive elements are-
They have a consistent number of particles
- the particles are alpha, beta and gamma particles.
They have a half-life that determines their rate of decay.
Explanation for other options:
Not all elements occur in nature. Radioactive decay rates may not be constant as the decay happens when a radioactive substance emits a particle. It is not possible to predict exactly when a given atom of a substance will emit a particular particle. When the radioactive element release energy and particles, it decays.
The cell membrane is semi permeable in nature, that is, it allows the passage of some substances while it disallows some substances. Small and non polar molecules pass quite easily through the cell membrane but large and polar molecules can not do this.
The substances which can easily pass through the cell membranes make use of passive transports such as diffusion and facilitated diffusion to enter the cells while substances which can not pass through the cell membranes on their own make use of active transport. Examples of active transport are endocytosis and ectocytosis,
QUESTION NUMBER ONE IS A AND FOR QUESTION NUMBER TWO IT IS B
Answer:
true
Explanation:
Cerebrospinal fluids is a colorless fluid that is secreted in the choroid plexus,and circulates in the ventricles system and sub -aranchinoid space of the brain and spinal cord. its provides nutrients to the surrounding neurons, cushions the effects of trauma, pressure, acts as buffer and provides protection through immune system .
it plays a vital role in regulating blood flow, through a process called cerebral auto regulation,This is needed to maintain efficient cerebral blood flow of oxygen and other metabolites, and withdraw of metabolic wastes from the brain.
in order to analyze it to diagnose some neurological diseases its sample is usually taken out in a process called lumbar puncture.
