Answer:
Jacob and Monod were intellectually primed to draw the conclusions they did concerning regulation of the lac operon. In part, this was due to their fascination with mechanisms of enzyme regulation. They knew that the activity of some enzymes is regulated when their reaction product binds to the enzyme, changing its shape and therefore its activity. This knowledge allowed them to easily make the intellectual leap to propose B) allosteric regulation of the repressor
Explanation:
When we talk about the mechanisms of enzyme regulation, we refer to allosteric regulation of the repressor. The Allosteric control of transcriptional regulatory proteins allows organisms to react to changes in environmental and metabolic conditions. Also, it is s a thermodynamic phenomenon. When it binds one molecule, the affinity with which a protein binds to a second molecule is altered.

<h2>Fixation</h2>
Nitrogen in its gaseous form (N2) can’t be used by most living things. It has to be converted or ‘fixed’ to a more usable form through a process called fixation. There are three ways nitrogen can be fixed to be useful for living things:
<h3>Biologically: </h3>
Nitrogen gas (N2) diffuses into the soil from the atmosphere, and species of bacteria convert this nitrogen to ammonium ions (NH4+), which can be used by plants. Legumes (such as clover and lupins) are often grown by farmers because they have nodules on their roots that contain nitrogen-fixing bacteria.
<h3>Through lightning: </h3>
Lightning converts atmospheric nitrogen into ammonia and nitrate (NO3) that enter soil with rainfall.

Answer:
The Presence of Liquid Water
Explanation: