Which tennis player became the first to claim the 100th ATP singles title of his career?

Introduction / Context:
In men professional tennis, ATP singles titles are a key measure of a player success and longevity. Winning 100 singles titles on the ATP Tour is an extraordinary achievement that only a very small number of players have approached. When a great champion reached his 100th ATP singles title, it became a widely reported milestone in sports news and is now a favourite question in general knowledge exams. This question asks you to identify which tennis player achieved this landmark.

Given Data / Assumptions:

• The focus is on ATP singles titles in men tennis.
• The milestone is reaching 100 ATP singles titles in a career.
• The options are Rafael Nadal, Andy Murray, Serena Williams, and Roger Federer.
• We assume standard ATP Tour records as maintained by the professional tennis circuit.

Concept / Approach:
The concept is recognition of a historic tennis career milestone. Roger Federer, one of the greatest tennis players of all time, reached his 100th ATP singles title at a tournament in Dubai, adding another record to his long list of achievements. Serena Williams, although a multiple Grand Slam champion, competes on the WTA Tour, not the ATP Tour, and the question is specifically about ATP titles. Rafael Nadal and Andy Murray also hold many titles but had not reached the 100 singles title mark at the time this milestone was celebrated. The correct approach is to remember that Federer is associated with this specific 100 titles headline.

Step-by-Step Solution:
Step 1: Interpret ATP singles titles correctly as men professional tour titles governed by the ATP. Step 2: Recall the group of top players with very high numbers of career titles: Roger Federer, Rafael Nadal, Novak Djokovic, and others. Step 3: Remember that Roger Federer was widely reported as reaching his 100th ATP singles title, a rare achievement in men tennis. Step 4: Note that Serena Williams, although exceptionally successful, plays on the WTA Tour and is not counted in ATP singles titles. Step 5: Recognise that Andy Murray, while highly accomplished, has far fewer than 100 ATP singles titles. Step 6: Select Roger Federer as the correct answer.

Verification / Alternative check:
To verify, recall the images and headlines from tennis news when this milestone was achieved. Reports showed Roger Federer lifting a trophy and celebrating the fact that he had reached 100 ATP singles titles, joining a very exclusive group of players in tennis history. Nadal and Murray, although very successful, are not associated with a similar 100 titles headline. Serena Williams statistics are tracked mainly on the women tour. This clear difference in media coverage confirms that the 100th ATP singles title belongs to Roger Federer.

Why Other Options Are Wrong:
Rafael Nadal: A multiple Grand Slam champion and one of the greatest clay court players, but he had not reached 100 ATP singles titles at the time this milestone was highlighted.

Andy Murray: Has won several big tournaments including Wimbledon and the Olympics, but his overall ATP singles title count is significantly lower than 100.

Serena Williams: A tennis legend on the women circuit with many WTA singles titles, but the question refers to ATP, which is the men tour, so this option does not match the requirement.

Common Pitfalls:
Sometimes candidates ignore the word ATP and choose Serena Williams because they think only of overall tennis greatness and not the difference between the men and women tours. Others may confuse Grand Slam counts with total titles and incorrectly assume that Nadal or another player reached the 100 mark in overall wins. To avoid these errors, pay attention to the exact phrase ATP singles title and recall that it is Roger Federer whose career achievements are closely linked to this 100 titles milestone.

Final Answer:
The tennis player who became the first to claim the 100th ATP singles title of his career is Roger Federer, so option D is correct.