"The fluidity of a biological membrane" is usually higher in plant cell membranes than animal cell membranes. is enhanced by the presence of cholesterol. increases with increasing temperature. is decreased when the proportion of unsaturated fatty acids is increased. describes the movement of water within the membrane double layer.

Of the mentioned statements, 1st and 2nd statements are correct.

Explanation:

With an increase in temperature, the fluidity of a cell membrane increases as the association between the phospholipids gets weakened with the increase in temperature that eventually encourages enhancement in the fluidity of the cell membranes.  

Also, with the increase in the concentration of cholesterol molecules, the fluidity of a biological membrane enhances, that is, at low temperature, cholesterol enhances the fluidity of the membranes by preventing the clustering of the phospholipids present in the membranes, and at greater temperatures, it reduces fluidity as it steadies the membrane and elevates its melting point.  

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.