Questions

The "aha!" experience is known as insight learning.

By trial and error method,

P=0, Q=9, R=0 satisfies the values.

Tuberculosis (TB) was the leading cause of death in the United States and one of the most feared diseases in the world during the 19th and early 20th centuries.

Formerly known as Consumption diseases because many types of lung diseases were lumped under the term 'consumption'. Lung cancer and bronchitis were examples.

The answer is EDUCATION

4,5,6 make up the word cat,

7th is 'i' which means me,

3rd letter is 'u' which mean you,

2,8,9,1 make up the word done, which means completed

and nobody can read without education.

The last line from the file "trial" would be read twice. To avoid this, ues:

       While ( fgets (str, 80, fp) ! = NULL)

               puts (str);

Molecular compounds are those with covalent bonds between the elements and those elements are typically non metals.

Here in the given options, Ar is an element. NaI has an ionic bond. Hence, N2O4 has a covalent bond between the two non metals and is a molecular compound.