select the significant figures in the measurement. 209.0 milligrams

Explanation:

Step1: Identify non - zero digits

Non - zero digits are always significant. In 209.0, 2, 9 are non - zero and significant.

Step2: Identify zeros between non - zero digits

Zeros between non - zero digits are significant. The 0 between 2 and 9 is significant.

Step3: Identify trailing zeros in a number with a decimal point

Trailing zeros in a number with a decimal point are significant. The 0 after 9 is significant.

Answer:

2, 0, 9, 0