The correct answer is option 1: 1826. The Treaty of Yandaboo was signed in 1826.

Now, let`s briefly examine the other options to eliminate any confusion. Option 2: 1825 is incorrect because the treaty was not signed in that year. Option 3: 1824 is also incorrect because the treaty was signed after that year. Option 4: 1823 is also incorrect because the treaty was signed after that year as well.

It is important to note that the Treaty of Yandaboo was a significant agreement between the British Empire and the Burmese Empire. The treaty was signed as a result of the First Anglo-Burmese War, which took place from 1824 to 1826. The treaty marked the end of the war and established certain conditions and terms between the two parties.

In conclusion, the Treaty of Yandaboo was signed in 1826, making option 1 the correct answer.