________ important thing it is to do eye exercises every day!

A) seldom B) always C) never D) sometimes

A) seriouser and seriouser B) more and more serious

C) more serious and more serious D) more serious and serious

A) badly B) well C) good D) bad

A) all B) both C) any D) either

A) Thousands of B) two thousands C) thousand of D) two thousands of

A) in B) at C) on D) of

A) himself B) he C) him D) his

A) a B) an C) / D) the

A. who is the abacus invented

B. when the abacus is invented

C. when was the abacus invented D. when the abacus was invented

A. was done B. will do C. can do D. can be done