### Instruction:

Extract the cause and effect entities from the following sentence:
Opportunities may arise during periods when the wide and deep surveys cannot be carried out in the nominal way

### Assistant:

VARIABLE: periods
CONDITION: be carried out in the nominal way
EFFECT_1: Opportunities may arise
KEYWORD: when
AND: and
NEGATION: cannot
CAUSE_2: the wide
CAUSE_3: deep surveys cannot be carried out in the nominal way
CAUSE_1: periods

