21.

NCERT Science textbooks for upper primary classes include large number of daily life-related questions which have been left unanswered. This has been done, so that

• teachers have a good pool of questions for assessment purpose

• students can send these questions to scientists to get the answer

• teachers can use these questions for home assignment

• students can seek answer to these questions by exploring different resources

While teaching the correct method of reading a clinical thermometer to Class VIII students, Neha mentions the following necessary precautions to be taken.
Which one of the following precautions has been mentioned wrongly by the teacher?

• Thermometer should be washed with hot water before and after use

• Do not hold the thermometer by the bulb while taking the reading

• Ensure that before use, the mercury level in the thermometer is below 35^oC

• Read the thermometer keeping the level of mercury along the line of sight

The section on 'activities and projects' included in the exercises of NCERT Science textbooks for Class VIII primarily aims at

• enhancing in-depth understanding of the basic concepts 

• keeping the students engaged during vacations

• assessing the students on practical skills

• providing opportunity to students for extended learning

Major objective of organization of Science Exhibitions is to

• grade students on practical skills

• provide opportunity to students to compete with others

• provide opportunity to students to showcase their creative ideas

• provide opportunity to students to enhance their academic performance

Four candidates appearing in an interview for the post of Science teacher were asked to give a demonstration lesson to class VIII students on the topic 'Pressure exerted by liquids and gases'. Following different approaches were followed by different candidates.
Which one of the following approaches will be most effective for teaching of the topic?

• Detailed explanation of related concepts with the help of diagram on the blackboard

• Use of charts for explanation of different concepts

• Organization of hands-on student activities followed up with discussions

• Greater focus on classroom questions during the lecture

The technique of 'classroom questioning' in teaching of Science can be more effectively used for

• ensuring levels of learning

• developing problem solving skills

• maintaining discipline in the class

• promoting creativity and innovativeness

Given below are the steps to test the presence of proteins in a food item. These steps are not incorrect sequence.

A. Take a small quantity of food item in a test tube add 10 drops of water to it and shake it.
B. Make the paste or powder of the food to be tested.
C. Add 10 drops of caustic soda solution to the test tube and shake well.
D. Add 2 drops of copper sulphate to it.

The correct sequence of these steps is

• A, B, D, C

• B, A, D, C

• B, A, C, D

• D, B, A, C

Which of the following terms constitute the female part of a flower?

• Stigma, ovary, and stamen

• Stigma, ovary, and style

• Stamen, ovary, and style

• Stamen, petals, and sepals

How many muscles work together to move a bone?

• Two

• Six

• Four

• Number is not fixed

Choose the set that represents only the biotic component of a habitat.

• Sand, turtle, crab, rocks

• Insects, frog, fish, aquatic plants

• Tiger, deer, grass, soil

• Insects, water, aquatic plants, fish