Multiple choice

Directions: Fill in the numbered blank (iv) with the best option from those given.

Directions: Fill in the numbered blank with the best option from those given.

Radium is a radioactive element. Let us see what “radioactive” _____ (i) ____. Radioactive elements do not change from year to year. But a few of the heaviest atoms break down and change into other kinds. This breakdown or ____ (ii) _____ is called “radio activity”. Each radioactive element _____ (iii) ____ by giving off rays at a certain rate. This rate cannot be _____ (iv) ____ or slowed down by any known method. Some changes occur rapidly, others slowly, but in all cases the action cannot be _____ (v) ______ by man.

  1. moved

  2. changed

  3. speeded up

  4. explained
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The text states the rate of radioactive disintegration "cannot be ____ or slowed down by any known method." The answer is "speeded up" - making it faster. "Moved" and "explained" don't fit the context of altering a rate. "Changed" is too vague; the sentence specifically discusses accelerating the rate.

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