Besides air and water, what would cause faeces to decompose faster?
It could be due to humidity, temperature or living organisms like worms, according to several science tutors.
This is an example of a "creative" question in this year's Primary School Leaving Examination (PSLE) science paper which experts say reflects the greater emphasis on getting pupils to apply what they learn in the classroom.
According to pupils and parents whose children took the exam on Tuesday last week, this year's paper was "interesting", "new" and "tricky".
It had at least five of such "creative" questions, which they had never come across in assessment papers and worksheets, they said.
For instance, the question on decomposition went beyond asking for definitions and explanations of the process, prompting pupils to think of factors that could speed it up.
This tests them on concepts like decomposition and interaction in the environment, said Mrs Amy Bellars, who owns Growan Learning Centre.
Another multiple-choice question asked how animal faeces would affect the amount of nutrients, fish, bacteria and plants in different parts of a river.
Such a question requires broader knowledge of concepts like interaction in the environment, photosynthesis and pollution, she added.
The science PSLE format consists of 30 multiple-choice questions and 14 open-ended ones.
Most parents and tutors The Straits Times spoke to said they were in favour of such application-based testing, as it helps children apply content rather than testing their memorising skills.
Mrs Bharti Daswani, 36, an associate lecturer whose Primary 6 daughter took the exam, said: "Science is exploratory in nature, so such questions are good."
Mee Toh Primary 6 pupil April Wong said: "It was more fun to answer these questions - even though there's a greater risk of losing marks - because I learnt something more.
"I tried my best to connect what I know to the questions."
Tutors like Mrs Summer Toh, 32, who set up The Water Family Enrichment Centre, also said they had received feedback from students that the science paper was more "interesting", but not overly difficult.
To prepare pupils for application-based testing, schools have been using a variety of methods, including hands-on experiments and field trips "so that they can see the relevance of science in everyday life", said a spokesman for the Ministry of Education.
"For example, students find out which materials are poorer conductors of heat, and collect and analyse data before making decisions on suitable materials to make containers for keeping drinks warm for a longer time," said the spokesman.
When contacted, the Singapore Examinations and Assessment Board said: "To answer the questions, students need to show their understanding and application of science knowledge and process skills within the syllabus."
Mrs Marie Hwang, 42, a housewife, said her son, who took the exam recently, had told her that every subject was "manageable".
Mrs Daswani said the mathematics paper was "fair", one that tested accuracy and knowledge learnt in school.
She said: "In some years, the maths papers had ridiculously hard questions, which made children lose confidence and hate the subject. No one I know has complained about maths so far, and I hope it stays this way."