11. Mac-Conkey medium is an example of

A. transport medium
B. enrichment medium
C. differential medium
D. all of these

12. Pseudomonas aeruginosa forms a blue water soluble pigment called

A. pyocyanin
B. chlororaphin
C. pyoverdin
D. β-carotene

13. Agar is used for solidifying culture media because

A. it does not affect by the growth of bacteria
B. it does not add to the nutritive properties of the medium
C. the melting and solidifying points of agar solution are not the same
D. all of the above

14. For the selection of lactobacilli present in cheddar cheese, the pH of the medium is maintained at

A. 6.35
B. 5.35
C. 4.35
D. 5.75

15. A disease producing species occurring in a mixed culture can often be selected on the basis of its

A. pathogenic properties
B. special carbon source
C. special nitrogen source
D. none of these