D. <span>controlled
is the right answer because a</span><span>n </span>experiment<span> in which an observer tests a hypothesis by looking for changes carried by alterations to a variable.</span>
<span>Vascular plants are able to grow higher than other plants due to the rigidity of xylem cells, which support the plant.</span>
Answer:
difference:
1. The generation mechanism is different, the mechanical wave is generated by mechanical vibration; the electromagnetic wave generation mechanism is also different, there is the periodic movement of electrons (radio waves); the outer electrons with atoms are generated after being excited (infrared, visible, ultraviolet) The inner electrons with atoms are generated after excitation (roentgen rays); the nuclei with atoms are generated after excitation (gamma rays).
2. The propagation mechanism is different: the mechanical interaction between the particles and the alternating induction of the electromagnetic field.
3. Mechanical waves have both transverse waves and longitudinal waves; electromagnetic waves are material waves and belong to transverse waves.
4. The influence of the medium on the propagation speed is different
Explanation:
https://qiaodahai.com/similarities-and-differences-between-mechanical-waves-and-electromagnetic-waves.html
Answer:
A
Explanation:
.............................spermatophytes...........................
