Concept:Multiplying decimals and writing the result in standard form.Explanation:Multiply 0.21 by 0.34.0.21×0.34=0.0714.To write this in standard form, place the decimal after the first non-zero digit: 7.14.The decimal point moves 2 places to the right, so the power of 10 is negative.Therefore, 0.0714=7.14×10−2.Answer:7.14×10−2, which is option B.