Question: What remembrance day held on April 25 features a riderless horse leading the march?
Sentence (from "Singaporean by-elections, 1961"): The first by election was held on 29 April 1961 and the nomination day was held on 11 March 1961 while the second by election was held on 15 July 1961 with the nomination day held on 10 June 1961.
Relevant evidence: No