A student recorded the bimonthly grades of some of his subjects in a table. He observed that the numerical entries in the table formed a $4 \times 4$ matrix, and that he could calculate the annual averages of these subjects using matrix multiplication. All tests had the same weight, and the table he obtained is shown below.
| $1^{st}$ bimonth | $2^{nd}$ bimonth | $3^{rd}$ bimonth | $4^{th}$ bimonth |
| Mathematics | 5.9 | 6.2 | 4.5 | 5.5 |
| Portuguese | 6.6 | 7.1 | 6.5 | 8.4 |
| Geography | 8.6 | 6.8 | 7.8 | 9.0 |
| History | 6.2 | 5.6 | 5.9 | 7.7 |
To obtain these averages, he multiplied the matrix obtained from the table by
(A) $\left[\frac{1}{2}\quad\frac{1}{2}\quad\frac{1}{2}\quad\frac{1}{2}\right]$