Wewerebusy________(get)thingsreadyforthetrialproductionwhenhephonedus.

heteachertoldthemsincelight________(travel)fasterthansound,lightning________(appear)togobeforethunder.

Wooddoesnotconductelectricity;________.

________(fail)severaltimes,theyneedsomeencouragement.

Ihavebeenstudyinghereforfouryears,bynextsummerI________.