Xylem is a plant tissue made up of elongated cells stacked end to end the length of the plant's stem. How does xylem help a plant survive? A) exchange gases with the atmosphere

B)pulls water and nutrients up the stem from the soil

C)collects sunlight for the plant to use during photosynthesis

D)transports glucose made during photosynthesis to cells throughout the plant

You are studying several alleles of an e. coli helicase gene. one allele, called rsr, confers resistance to rs2014, an antibiotic that works by inhibiting helicase activity. bacteria with the rss allele are sensitive to rs2014. another allele, called ts-, produces a temperature sensitive mutation of the helicase. in bacteria with the ts- allele, helicase is inactivated at 42 °c but functions normally at 37 °c. helicase functions normally at both temperatures in bacteria with the ts allele. you obtain the following data while testing four strains of e. coli at different temperatures and doses of rs2014. each number represents the percentage of maximal dna synthesis. based on this data, assign the appropriate genotype to strains a–d in the spaces provided