1. An extract of the bark of the Indian fig tree, Ficus racemosa, has antioxidant properties. It has been suggested that this extract could protect against damage to non-cancerous cells during radiotherapy.

Cultures of non-cancerous cells were exposed to increasing doses of radiation and the percentage of damaged cells was measured. The experiments were performed multiple times either with or without the bark extract.

The graph shows the results for the two sets of data. Each data point shows the mean ±1 standard deviation.

A student used Spearman’s rank correlation coefficient to test for correlation between radiation dose and cell damage.

Which of the following statements, A to D, about this correlation shown on the graph is correct?