hard at it

词形变化：

形容词比较级: harder | 形容词最高级: hardest |

同义词：

difficult | firm | intensely | fast | violently | fiercely | powerfully | rigorously | relentlessly | remorselessly | intense | severe | cruel | arduous | stern | tough | rigid | strict | unyielding | stony | rugged | solid | harsh | inflexible | ugly | rough | callous | unpleasant | strenuously | strong | complicated | laboriously | troublesome | iron | marble | resistant | painful | rigorous | stiff | wicked | afflictive | exacting | exigent | strenuous | relentless | formidable | wretched | violent | with effort | soft | with | effort | easy | vigor | heavy | operose | heavily | concentrated | toilsome | laborious | backbreaking | simple | unvoiced | punishing | grueling | severely | gruelling | surd | voiceless | firmly | intemperately | knockout | intemperate |

反义词：

soft |