Who won the Academy Award for Best Actor at the 90th Oscars ceremony held in 2018?

Introduction / Context:
The Academy Awards, commonly known as the Oscars, are an important part of international current affairs and film related general knowledge. Questions about specific Oscar winners are frequently asked in exams. This question deals with the 90th Academy Awards ceremony, held in 2018, and asks who won the Best Actor award. The correct answer is Gary Oldman, who received the award for his portrayal of Winston Churchill in the film Darkest Hour. Remembering such high profile winners helps in quick fact based scoring.

Given Data / Assumptions:
- The event is the 90th Academy Awards ceremony. - The year of reference is 2018. - The category is Best Actor. - The options list well known actors who were either nominees or prominent around that time.

Concept / Approach:
To answer, one must recall the list of winners at the 90th Oscars. A useful method is to link each actor with the major film they were associated with that year. Gary Oldman delivered a widely praised performance as Winston Churchill in Darkest Hour, which was heavily discussed in media and award forecasts. The Oscars that year rewarded his transformation and acting range. Denzel Washington, Daniel Day Lewis, Daniel Kaluuya, and Timothee Chalamet were also nominated in different categories or years, but none of them won Best Actor at that particular ceremony. By mapping each name to their actual awards and nominations, we can confidently select the correct option.

Step-by-Step Solution:
1. Identify that the question is about the 90th Oscars, which took place in 2018. 2. Recall that Gary Oldman won the Best Actor award that year for his role in Darkest Hour. 3. Note that other strong performances and nominees included actors like Daniel Day Lewis and Timothee Chalamet but they did not win. 4. Scan the options and find Gary Oldman listed among them. 5. Select Gary Oldman as the Best Actor winner for this specific ceremony.

Verification / Alternative check:
A quick verification approach is to recall images or headlines from entertainment news websites or newspapers after the 2018 Oscars. Many of them highlighted Gary Oldman receiving the Oscar and giving a memorable acceptance speech. Darkest Hour was also strongly promoted in award prediction articles, making this pairing easier to remember. Candidates can additionally recall that Frances McDormand won Best Actress the same year for Three Billboards Outside Ebbing, Missouri, which further anchors the memory of that ceremony. This cross linkage supports the answer that Gary Oldman was the Best Actor awardee.

Why Other Options Are Wrong:
Denzel Washington is a highly acclaimed actor and has won Oscars earlier, but he did not win the Best Actor award at the 90th Academy Awards in 2018. Daniel Day Lewis is one of the most respected actors in cinema history, but he did not secure the Best Actor trophy for that particular year. Daniel Kaluuya received significant attention for his performance in Get Out, yet he did not win the Best Actor Oscar at this ceremony. Timothee Chalamet is a talented young actor who gained recognition for Call Me by Your Name, but he was only a nominee and not the winner in 2018.

Common Pitfalls:
Students often confuse nominees with winners, especially when several strong performances compete in the same year. Another common issue is mixing up different award shows such as the Golden Globes, BAFTA Awards, and the Oscars, where the winners may differ. Exam takers may also remember that these actors have all been nominated or awarded at some point and mistakenly associate the wrong year or category with the question. To avoid this, it is helpful to create a short summary for major Oscar ceremonies, listing Best Film, Best Actor, and Best Actress, and revising those lists just before the exam.

Final Answer:
At the 90th Academy Awards in 2018, the Best Actor award was won by Gary Oldman.