Explanation:
The circulatory and respiratory systems work together to circulate blood and oxygen throughout the body. Air moves in and out of the lungs through the trachea, bronchi, and bronchioles. Blood moves in and out of the lungs through the pulmonary arteries and veins that connect to the heart.
A hypothesis is considered scientific if it has something that can be supported or refuted through carefully crafted experimentation or observation
<span>The gene sequence containing an operator, promoter and repressor is known as an operon. These genes are called as structural genes. the operon is regulated by the presence/absence of the inducer such as glucose/lactose. It may also be a constitutive operon, which works all the time.</span>
Metaphase
I remember it has meta = middle
B. going to be refined by further investigation
thats the answer because you need proof that the theroy is wrong