Answer: D. 65536.
Answer analysis: In a grayscale image, the grayscale level represents the brightness level of the pixel in the image. For a 16-bit grayscale image, each pixel uses a 16-bit binary number to represent its grayscale value.
The representation range of binary numbers is from 0 to 2^n - 1, where n is the number of bits of the binary number. Therefore, for a 16-bit grayscale image, its grayscale value ranges from 0 to 2^16 - 1.
Calculate the value of 2^16 - 1:
2^16 - 1 = 65536 - 1 = 65535
But it should be noted here that the number of grayscale levels is counted from 0, so there are actually 65536 levels, including the darkest (0) to the brightest (65535).
However, the question asks "how many levels are there from the darkest to the brightest", which is actually asking how many different grayscale values there are, that is, 65536.
Comparison options:
A. 1024 is 2^10, which does not match the number of grayscale levels of 16Bit.
B. 4096 is 2^12, which also does not match.
C. 16384 is 2^14, which also does not match.
D. 65536 is 2^16, which matches our calculation results.
So the answer is: D. 65536. But it should be noted that although the answer is 65536, the question asks about the number of "levels", and in fact this number includes all values from 0 to 65535, a total of 65536.