Bacterial Size in Meters

Steps:

• Recall that prokaryotes like Streptococcus have diameters of 0.5–5 μm.
• Convert 0.75 μm to meters: 1 μm = 10^{-6} m, so 0.75 μm = 7.5 × 10^{-7} m.
• Match this to the choice with the correct scientific notation and unit.
• Eliminate options with incorrect units or exponents.

Why B is correct:

• Bacterial diameters are typically 10^{-6} to 10^{-5} m, and 7.5 × 10^{-7} m equals 0.75 μm, matching standard prokaryote size per microbiology definitions.

Why the others are wrong:

• A: 7.5 × 10^{-6} m is 7.5 μm, too large for most bacteria.
• C: 7.5 × 10^{-6} μm is 7.5 × 10^{-12} m, nanoscale and unrealistic for cells.
• D: 7.5 × 10^{-7} μm is even smaller at 7.5 × 10^{-13} m, far below prokaryote dimensions.

Final answer: B