Both ‘Delay’ and ‘Retard’ mean to slow down progress or make something happen later than expected. They are synonymous in nature.

১. ‘Slow down’ and ‘hold up’ also mean to cause a delay or impede progress, making this the correct pair.
২. ‘Postpone’ and ‘promote’ are not synonyms; one means to delay and the other means to advance or support.
৩. ‘Defer’ and ‘accelerate’ are antonyms, as accelerate means to move faster.

অতিরিক্ত তথ্য: ‘Retard’ is often used in technical contexts to describe slowing down a reaction or process.