Question

1. why did the e. coli i strain grow on both the lb agar plate and the lb agar plate with streptomycin but not grow on the lb agar plate with ampicillin?

Explanation:

The E. coli I strain likely has resistance to streptomycin, allowing growth on LB - streptomycin plate and normal LB plate. It lacks resistance to ampicillin, hence no growth on LB - ampicillin plate. Resistance can be due to genetic factors like plasmids carrying resistance genes.

Answer:

The E. coli I strain is resistant to streptomycin but sensitive to ampicillin.