Answers (a) and (c) have
3º or 4º between temperature and dew point and the trend is
NOSIG.
Answer (d) has the
visibility temporarily reducing to 1,500m but returning to 4,000m.
The remaining answer
shows only one degree between temperature and dew point and the visibility
falling from 6,000m to 1,600m in mist; it is likely to thicken to fog through
the night.