Read the paragraph below to answer question.

An increased incidence of kidney stones and renal failure in infants has been reported in China, believed to be associated with the ingestion of infant formula contaminated with melamine. It has been discovered that melamine has been deliberately added to raw milk for a number of months in order to boost its apparent protein content. In 2007 there was a large outbreak of renal failure in cats and dogs in the USA associated with ingestion of pet food found to contain melamine and cyanuric acid. Melamine alone is of low toxicity; experimental studies have shown that combination with cyanuric acid leads to crystal formation and subsequent kidney toxicity.

Choose the alternative that fills in correctly the blank of the sentence below.

“Melamine alone is of low toxicity; experimental studies have shown that combination with cyanuric acid leads to crystal formation and subsequent kidney toxicity”.

World Health Organization, 30/10/2008.