Read the passage and choose the correct answer for the following questions:

All at once Hazel was coming in through the French windows, pulling off gardening gloves, and Bill was entering through the door, both at once. So I only had time to take one quick look at her before I turned to face him. All very confusing. What that first glimpse showed me was that time had thickened her figure but didn’t seem to have made much difference to her face. It still had good skin and youthful outlines. She was holding a bunch of roses – must have been cutting them in the garden while waiting for me. The gardening gloves lent a delightfully informal touch. It was quite an entrance, though Bill spoilt it a bit by making his at the same time. Bill seemed longer and thinner. His tightly massed hair had a tinge of grey. Apart from that, twenty years had done nothing to him, except deepen the lines of thoughtfulness that had already, when I knew him, begun to spread across his face. Or was that all? I looked at him again, more carefully, as he looked away from me at Hazel. Weren’t his eyes different somehow? More inward looking than ever? Gazing in not merely at his thoughts, but at something else, something he was keeping hidden or perhaps protecting. Then we were chattering and taking glasses in our hands, and I came back to earth. For the first ten minutes we were all so defensive, so carefully probing, that nobody learnt anything. Bill had forgotten me altogether, that much was clear. He was engaged in getting to know me from scratch, very cautiously so as not to hit a wrong note, with the object of getting me to contribute a big subscription to his African project. I kept trying to absorb details about Hazel, but Bill was talking earnestly about African education, and the strain of appearing to concentrate while actually thinking about his wife proved so great that I decided it would be easier just to concentrate. So I did. I let him hammer away for about ten more minutes, and then the daughter, who seemed to be acting as parlourmaid, showed in another visitor. Evidently we were to be four at lunch.

Tropical diseases are comparatively ….. in Europe. A. scarce B. rare C. slight D. few