Read the sentence to find out if there is an error and choose the corresponding answer:

A. Climatic shifts are
B. so gradual they can be
C. indistinguishable at first
D. from ordinary fluctuations
E. in the weather

Choose the correct answer from the options given below:

B only

The correct answer is Option (1) - B only

The error is in part B. The construction "so [adjective] that..." is needed to correctly form the sentence. In this case, part B should read "so gradual that they can be" to connect the cause ("climatic shifts are so gradual") with the effect ("they can be indistinguishable...").