Explain how the hard, bony body of a seahorse could be an advantage.
The right answer, according to one Primary 6 science teacher, is: "It protects the seahorse from injury and reduces the chances of predators successfully feeding on it."
But the child who wrote "It acts as an armour that protects the seahorse from predators" was told that her answer was wrong.
This was one of several examples thrown up by parents, who have complained recently that primary school science teachers are too rigid in marking open-ended questions, and are emphasising rote learning over the understanding of concepts.
This, despite schools having shifted to an inquiry-based learning approach in science since 2008. With the approach, pupils are encouraged to ask questions, analyse data and come to their own conclusions.
Several parents wrote to The Straits Times Forum page earlier this month, calling for schools to be more flexible. Most said their children were unduly penalised for answers that had the same meaning as the correct ones, but did not contain the right "key words".
The children had been told by teachers to stick to key phrases and words found in textbooks, in order to get full marks in assignments or tests.
On top of those who wrote in, nine in 10 parents contacted by The Straits Times felt that the teachers have been overly strict.
Psychologist Inez Perera, 49, whose daughter was in Primary 6 last year, recalled: "She had to memorise so many model answers. Some made sense, but does it have to be so rigid?"
Ms Elizabeth Tan, whose son is in Primary 6, said he resorted to writing key phrases and sentences repeatedly to remember them for his examinations.
"You're teaching children that there's only one answer for every question, and they can't think out of the box," said the 41-year-old housewife.
"Children are meant to explore ideas and discover things in science... but it seems key words are more important."
But others, including mother of three Tracy Ng, 41, felt that precision in learning the language of science was important.
"It's part of building up a foundation in science education so that there's no misunderstanding of concepts," said the sales manager in a pharmaceutical company.
Five teachers spoken to said that they decide which answers can be accepted after group discussions.
But one primary school teacher, who has taught science, mathematics and English in the past decade, admitted that even teachers themselves have different points of view when it comes to how answers should be worded in science tests.
"It's quite controversial because language comes into play," said the teacher, who declined to be named.
"But in the end, the head of department for science will still have to make the call on the accepted answer."
One such department head, who also wanted to remain anonymous, said: "Schools may come up with slightly different marking schemes, so it depends on how lenient each school is."
But she pointed out that "regurgitating" answers will not work, as science questions in the Primary School Leaving Examination have become more application- based in recent years.
"We're fine-tuning questions to link them to real-life situations," she said.
"It's not about key words, but showing that they understand concepts."
In response to queries, the Singapore Examinations and Assessment Board and the Ministry of Education said that answers that "show evidence of understanding of relevant concepts and mastery of skill sets would be carefully evaluated and awarded due credit".
Said a spokesman for both the exam board and the ministry: "Answers that deviate from the marking scheme but demonstrate the right understanding are accepted.
"On the other hand, the marking must be robust enough to exclude conceptually flawed or ambiguous responses."