$ \begin{array}{|c|c|c|}\hline
\textbf{Task}&\textbf{Profit}&\textbf{Deadline}\\ \hline
T_3&30&5&\checkmark \\ \hline
T_9&25&3&\checkmark \\ \hline
T_7&23&2&\checkmark \\ \hline
T_2&20&2&\checkmark \\ \hline
T_5&18&4&\checkmark \\ \hline
T_4&18&3& ✗ \\ \hline
T_8&16&7&\checkmark \\ \hline
T_1&15&7&\checkmark \\ \hline
T_6&10&2& ✗ \\ \hline
\end{array}$
Step -1 Sort the tasks in decreasing order of profit and if any conflict arises between two or more tasks,resolve them by sorting them on basis of having greater deadline first(Because we have more time to complete the task with greater deadline and same profit).
Step 2- Since Maximum deadline given is $7$, so we consider we have 7 time slots ranging from $0-7$ where a task $T_i$ having deadline say $2$ can be filled in slots either $0-1$ or $1-2$ and not beyond $2$ because this task has deadline of $2$ time units, so this task has to be completed by at most time $T=2$.
Now according to question, since Each task completes in Unit time, so a single tasks takes only one slot as shown.
Now Take the first task in the list i.e. $T_3$ which has a deadline of $5$, so it can be completed in maximum $5$ time units, so place it in slot $4-5$ which is the maximum deadline by which this task can be completed.
Task $T_9$ with deadline $3$ is similarly placed in slot $2-3$.
Task $T_7$ with deadline $2$ is placed in slot $1-2$.
Now for task $T_2$ having deadline $2$ can be placed in either $0-1$ or $1-2$ (Occupied by $T_7$). So $T_2$ will occupy slot $0-1$.
Task $T_5$ with deadline $4$ is placed in slot $3-4$.
Now comes task $T_4$ which has deadline $3$ can be put in slots $0-1$ or $1-2$ or $2-3$ and not beyond that.Unfortunately, all such slots are occupied so $\bf{T_4}$ will be left out.
Task $T_8$ with deadline $7$ goes in slot $6-7$.
Task $T_1$ with deadline $7$ can be placed in slot $5-6$.
Now all time slots are full.
So, Task $\bf{T_6}$ will be left out.
So, option (d) is the answer.