To find the value of D, we need to sum the terms of the given sequence.

The sequence starts with 2 and alternates between adding and subtracting 2. So, the common difference is -2.

We can write the sequence as follows:

2, -2, 6, -8, ..., -96, 98

To find the sum of this arithmetic sequence, we can use the formula for the sum of an arithmetic series:

Sn = (n/2)(a1 + an)

where Sn is the sum of the first n terms, a1 is the first term, and an is the nth term.

In this case, a1 = 2 and an = 98.

We need to find the value of n. The nth term can be found using the formula:

an = a1 + (n-1)d

where d is the common difference.

In this case, an = 98 and d = -2.

98 = 2 + (n-1)(-2)
98 = 2 - 2n + 2
98 = 4 - 2n
2n = 4 - 98
2n = -94
n = -94/2
n = -47

Since n cannot be negative in this context, we can conclude that there is a mistake in the given sequence.

If we assume that the sequence starts with 2 and alternates between adding and subtracting 4, then the sequence would be:

2, -2, 6, -10, 14, -18, ..., -94, 98

In this case, the common difference is -4.

Using the same formula as before, we can find the value of n:

98 = 2 + (n-1)(-4)
98 = 2 - 4n + 4
98 = 6 - 4n
4n = 6 - 98
4n = -92
n = -92/4
n = -23

Again, since n cannot be negative in this context, we can conclude that there is a mistake in the given sequence.

Please provide the correct sequence so that we can find the value of D.