Who was invited to be the chief guest at the Republic Day parade of India in 2019?

Introduction / Context:
Every year, India invites a foreign head of state or government as the chief guest for the Republic Day parade held on 26 January in New Delhi. This tradition reflects India's diplomatic priorities and friendships. The question tests awareness of international relations and current affairs by asking who was the chief guest for the Republic Day celebrations in 2019.

Given Data / Assumptions:
- The event is India's Republic Day parade in 2019.
- The question asks for the name of the foreign leader invited as chief guest.
- Four world leaders are listed: Donald Trump, Cyril Ramaphosa, Theresa May, and Scott Morrison.
- Only one of these leaders actually attended India's Republic Day celebrations in 2019 as chief guest.

Concept / Approach:
In 2019, India invited Cyril Ramaphosa, the President of South Africa, as the chief guest for Republic Day. This invitation highlighted the close historical and strategic ties between India and South Africa, including cooperation within groupings such as BRICS. The other leaders listed were heads of state or government of other countries around the same time, but they were not the chief guests in 2019.

Step-by-Step Solution:
Step 1: Recall from current affairs that India has often invited leaders from Africa, ASEAN, Europe, and other regions as Republic Day chief guests. Step 2: Focus on the year 2019 and remember that Cyril Ramaphosa of South Africa visited India as the chief guest. Step 3: Examine the options: Donald Trump (United States), Cyril Ramaphosa (South Africa), Theresa May (United Kingdom), Scott Morrison (Australia). Step 4: Confirm that news reports of 2019 Republic Day celebrations specifically mentioned President Cyril Ramaphosa as the chief guest. Step 5: Select Cyril Ramaphosa as the correct answer.

Verification / Alternative check:
A quick cross check is to recall that leaders from the Association of Southeast Asian Nations were special guests in 2018, while 2019 shifted focus back to a single chief guest from South Africa. Additionally, exam preparation materials and yearbooks often list the Republic Day chief guests for each year, and for 2019 they consistently show Cyril Ramaphosa.

Why Other Options Are Wrong:
Donald Trump: The United States President did not attend India's Republic Day parade in 2019 as chief guest.
Theresa May: The British Prime Minister was not invited as chief guest in that particular year.
Scott Morrison: The Australian Prime Minister did not serve as Republic Day chief guest in 2019.

Common Pitfalls:
Learners may be tempted to pick very famous names like Donald Trump without checking the specific year and event. Another pitfall is mixing up the chief guest for Republic Day with leaders who visited India for other summits or bilateral meetings. Keeping a short list of Republic Day chief guests by year can help avoid such confusion in competitive exams.

Final Answer:
Therefore, the chief guest at India's Republic Day parade in 2019 was Cyril Ramaphosa.