A botanist recorded the following fresh masses of a plant shoot over five weeks: Week 0 = 4 g, Week 1 = 8 g, Week 2 = 16 g, Week 3 = 32 g, Week 4 = 64 g. Which mathematical expression correctly represents the growth pattern observed, where $M_t$ is mass at time $t$ weeks and $M_0$ is the initial mass?

The data shows the mass doubling every week (4→8→16→32→64), which is exponential growth. The correct expression is $M_t = M_0 \times 2^t$, giving 4×2¹=8, 4×2²=16, 4×2³=32, and 4×2⁴=64, all matching the data. Option A represents linear (arithmetic) growth, which would give 8, 12, 16, 20 — not matching. Option C gives 4, 16, 36, 64 — inconsistent. Option D is dimensionally inconsistent and does not fit the data.