4. A fruit tree planting base has adopted two measures, expanding the planting scale and scientific management, to continuously meet market demand. In recent years, the amount of fruit supplied to the market has been: 46 t in 1998, 58 t in 2000, and 75 t in 2002. According to predictions, within a certain period, the fruit supply volume \( y \) t of the fruit tree planting base and the year number \( x \) satisfy a quadratic function relationship. Therefore, the predicted fruit supply volume in 2004 is \((\quad) \) t.
(A) 85
(B) 92
(C) 97
(D) 100
4.C.

For convenience, let 1998 be the starting year for calculation, with the year number as 0, and assume the predicted fruit supply in 2004 is $M \mathrm{t}$, and the quadratic function we are looking for is $y=a x^{2}+b x+c$.

From the problem, we know that the points $(0,46) 、(2,58) 、(4,75) 、(6, M)$ all lie on the graph of this quadratic function. Therefore, we have
$$
\left\{\begin{array}{l}
c=46, \\
4 a+2 b+c=58, \\
16 a+4 b+c=75 .
\end{array}\right.
$$
Solving these equations, we get $a=\frac{5}{8}, b=\frac{19}{4}, c=46$.
Thus, $M=\frac{5}{8} \times 6^{2}+\frac{19}{4} \times 6+46=97(\mathrm{t})$.