Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions.

The first vehicle that resembled the bicycle was put together in 1645 in France by Jean Theson. It was, however, a four-wheeled machine. A two-wheeled contraption was invented in Germany in about 1816. To ride it, the passenger sat on a seat and propelled himself by running on the ground.

The two-wheeled bicycle as we know it today was invented in Dumfriesshire, Scotland, in 1839 by a blacksmith named Kirkpatrick Macmillan. It had a steerable 30-inch front wheel and a 40-inch rear wheel. This bicycle had no pedals or chain-activated gears. There were, instead, two foot pedals attached to rods that connected to the back wheel. The alternate movement of rods on either side propelled the bicycle.

Unfortunately for Macmillan, his invention never became popular. It was left to a French father-and-son team, Pierre and Ernest Michaux, to build the bicycle from which the present popularity of the vehicle is derived. By 1865 the Michaux family was producing 400 bicycles a year.

The doctor decided to give her a thorough examination _____________ he could identify the causes of her illness. A. unless B. after C. so as D. so that