Which of the following describes humidity? The temperature of the air
The weight of the air pressing down on you
The amount of water vapor in the air
The direction the wind is blowing

Humidity describes the amount of water vapor in the air, and the more water vapor that is present, the more humid it is. ... This is the amount of water vapor in the air relative to what the air can hold. This is just like figuring out how much water is in a cup relative to the total amount of water that cup can hold.

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.

the answer is; comparing the frequency of collisions with and without the device

this makes the anti-collision system an independent variable and the collisions a dependent variable. if there are fewer collisions with an anti-collision system that without, then it can be stated that the system is a success. essentially, collisions under an anti-collision system are compared with the frequency of collisions by cars with the human drivers.