A spherical rain drop evaporates at a rate proportional to its surface area. If initially its radius is 3 mm and after 1 second it is reduced to 2 mm , then at any time t its radius is (where $0 \leq \mathrm{t}<3$)
- A$\mathrm{3+t}$
- B$3-\mathrm{t}$
- C$4-\mathrm{t}$
- D$1+\mathrm{t}$
✓ Correct answer: B
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