Multiple choice

Directions: Fill in the numbered blank (ii) 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. tear off

  2. failure

  3. decay

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

The text describes how heavy atoms "break down and change into other kinds" and calls this process "radioactivity." This breakdown is scientifically called "decay" - radioactive decay. "Tear off" is too informal, "failure" doesn't describe the transformation process, and "build up" is the opposite of what happens.

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