Fast all points i got plus its not an a, b,c, d question i need to answer it the double helix structure of the dna looks like a ladder. which parts create the rungs? which parts hold the rungs together?

The model is called a double helix because two long strands twist around each other like a twisted ladder. The rails of the ladder are made of alternating sugar and phosphate molecules. The steps of the ladder are made of two bases joined together with either two or three weak hydrogen bonds.

DNA is basically a long polymer of nucleotides. It's backbone is made of sugars and phosphate groups joined by ester bonds. Attached to each sugar is one of four types of molecules called bases, or the rungs. The 4 bases for DNA are Adenine, Thymine, Guanine, & Cytosine. Adenine and Thymine is a base pair and form two H-bonds. Guanine and Cytosine is the other base pair, but forming three H-bonds. These H-bonds stabilize the two helices.

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.