All of the following statements are true regarding Staphylococci except -
"Methicillin resistance is expressed more at 30°C than at 37°C", so susceptibility studies for methicillin are routinely performed at reduced temperature (30° - 35° C for 24 hrs), with increased concentration of salt in the medium to enhance the expression of resistance.
Resistance to antibiotics 

Penicillin resistance is of three types-

1) Production of beta-lactamase (penicillinase)

It inactivates penicillin by splitting β-lactam ring
Its production is controlled by plasmid.
Plasmid is transmitted by transduction (mainly) or conjugation.
Penicillinase is an inducible enzyme


As a result of the widespread dissemination of plasmids containing penicillinase, less than 5% strains of staph. remain susceptible to penicillin.
Staphylococci produce four type of penicillinases, A to D. Hospital strains usually forms type 'A' penicillinase.

2) Changes in bacterial surface receptors by lack or inaccessibility of certain penicillin binding proteins (PBPs) in the organism.

Methicillin resistant is mainly due to this mechanism and is independent of β - lactamase production.
It is due to production of PBP 2a.
This change (in bacterial surface receptors) is normally chromosomal in nature.
The resistance gene is mec A gene which is a part of large mobile genetic element - staphylococcal cassette chromosome (SCCmec).
This genetic material has been transferred to Staph. aureus from S. seiuri.

3) Development of tolerance to penicillin, by which the bacterium is only inhibited but not killed.
About option 'a'
"Approximately 75% of the infections caused by coagulase negative staphylococci are due to staphylococcus epidertnidis" -
A majority of infections caused by coagulase-negative Staphylococci are due to Staphylococcus epidermidis
β-lactamase production in Staphylococci is under plasmid control
Expression of methicillin resistance in Staphylococcus aureus increases when it is incubated at 37°C on blood agar.
Methicillin resistance in Staphylococcus aureus is independent of β-lactamase production