**Core Concept**
Gram-positive cocci are a group of bacteria characterized by their thick peptidoglycan cell walls and gram-positive staining properties. This group includes various species such as Staphylococcus, Micrococcus, Streptococcus, and Enterococcus, each with distinct clinical significance and antimicrobial susceptibility patterns.

**Why the Correct Answer is Right**
Most enterococci are resistant to penicillin due to the presence of beta-lactamase enzymes, which inactivate the antibiotic. This resistance is a significant concern in the treatment of enterococcal infections, particularly in hospitalized patients. As a result, alternative antibiotics such as ampicillin, vancomycin, or linezolid are often required for effective treatment. The expression of beta-lactamase enzymes is a key factor in the development of penicillin resistance in enterococci.

**Why Each Wrong Option is Incorrect**
**Option A:** Staphylococcus saprophyticus is indeed a cause of urinary tract infections (UTIs) in females, particularly in young women. This option is true and not false.
**Option B:** Micrococci are indeed oxidase positive, which is a characteristic feature used to differentiate them from other gram-positive cocci. This option is true and not false.
**Option D:** Pneumococci (Streptococcus pneumoniae) are indeed capsulated, with the capsule being a key virulence factor that contributes to their ability to cause invasive infections. This option is true and not false.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that enterococci are often resistant to multiple antibiotics, including penicillin, and may require the use of combination therapy or alternative antibiotics to achieve effective treatment.

**✓ Correct Answer: C. Most enterococci are sensitive to penicillin**