Consider the C struct defined below:

struct data{
 int marks [100];
 char grade;
 int cnumber;
 };
struct data student;

The base address of student is available in register R1. The field student.grade can be accessed efficiently using

Options:
(A) Post-increment addressing mode, (R1)+
(B) Pre-decrement addressing mode, − (R1)
(C) Register direct addressing mode, R1
(D) Index addressing mode, X(R1), where X is an offset represented in 2’s complement 16-bit representation.