Sir iknow we use had when we want to tell two incidences in the past...eg..the train had left the station before I reached station...thats fine...now my question is...I want to write a up and down tend in a line graph at different duration...assume I used simple past tense in the first two sentences in a paragraph..now in the third sentence..I write"the oil price had plunged to 200 barrels in 2000 before it surged to 600 barrels in 2005". Or should I write without "had"...I want to know here had is optional or not?.plzzzzzzz help me