Nature's news quiz: chemical elements, Planet Nine, and a nuclear test.

1. You and your microbes

Bacteria in the human body outnumber our own cells by what ratio, according to an estimate published this month?

2. Chemical elements

Scientists from Japan, the United States and Russia are considering what to call the newest confirmed elements in the periodic table – numbers 113, 115, 117 and 118. But there are rules on naming elements: what can’t they be named after?

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