【正确答案】 B

【答案解析】[解析] 划线词为形容词，意思是“安全的，受保护的”，与B项(可靠的，牢固的)为同义词，又如：That is a secure foothold．那是一个可靠的落脚点。A项意为“黑暗的”，例：That was a dark，moonless night．那是一个黑暗的、无月光的夜晚。C项意为“(言论等)谨慎的”，例：Their carefully guarded secret was soon common property in the company．他们小心，翼冀保守的秘密很快就在公司传开了。D项意为“禁止的”，例： Maybe Watson had no intention to win by taking，banned substance。也许沃森并不是有意要想通过服违禁物来赢得比赛。