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.
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.
a reasonably clear picture has emerged of the patterns and causes of ocean currents
a reasonably clear picture of the patterns of ocean currents and their causes have emerged
a reasonably clear picture emerged of ocean currents, their patterns and the causes of them
there have emerged a reasonably clear picture of the patterns of ocean currents and what caused them
there had emerged a reasonably clear picture of the patterns of ocean currents and their causes
Answer: A
of the patterns and causes of ocean currents为什么放在emerge后面呀?
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。