511. For several years his ambition B. has been to be a pilot. 512. Henry B. went into the restaurant when the writer was having dinner. 513. He will take the dog out for a walk as soon as he B. finishes dinner. 514. Before you asked, the letter B. had been written. 515. Ask her to come and see me when she B. has finished her work. 516. Oil B. floats if you pour it on water. 517. The dancing club B. lies north of the city. 518. Almost everyone D. had left for home by the time we arrived. 519. By the age of 25, he D. had written two famous novels. 520. While her husband was in the army, Janet B. wrote to him twice a week.