Navigators have known for thousands of years that the ocean has variable currents, but it is only in the last half century that a reasonably clear picture has emerged of the patterns and causes of ocean currents.
B.(a reasonably clear picture of the patterns of ocean currents) and (their causes) have emerged
用have改变原文的意思,变成了picture和causes的并列。即便改成has,their的指代仍然错。A表达清晰不含歧义。 |