Cross my heart:
穿过我的心 ×
我发誓是真的 √
例句:
Billy, cross my heart, it wasn't me who broke your bicycle.
Billy,我发誓, 不是我损坏你的自行车。
A heart of stone:
铁石心肠 √
例句:
His enthusiasm is enough to melt a heart of stone.
他的热诚足以软化铁石心肠。
Heart and soul:
心和灵魂 ×
全心全意,一心;竭诚 √
例句:
"I will put my heart and soul into the job," he promises.
“我会全身心投入到工作中去,”他保证说。