The medicine will-- you a good night's sleep. guarentee or ensure?

[on the way]

Recently I came across a multiple choice which goes as follow:
Don't worry.The medicine will --- you a good night's sleep.
A. assure B. ensure C. guarantee D. secure
As far as I understand ,neither "assure" or "secure" is appropriate here .What puzzles me is that "guarantee" and "ensure" can both mean "make certain something will happen ",which seemingly,at least for me ,makes either of them suitable here.So I'm dying for some clearing-up here .I would appreciate any help here.Thank you all.

[abaka]

Guarantee, I think.

Otherwise the patterns are something like

I assure you, with this medicine you'll get a good night's sleep.

This medicine will ensure you'll get a good night's sleep. (Some might say this sentence is a little sloppy, and "make sure" is better.)

This medicine will secure a good night's sleep for you.

[Rover_KE]

I agree that guarantee is the best answer to what is not a good question.

For ensure to be right I would expect the sentence to read 'This medicine will ensure that you get a good night's sleep.

Please note, on the way, that we leave a space after a full stop, comma and question mark — not before it.


​Rover

[on the way]

Thank you all!It's really a great place to improve our English.Thank you all again!

[Rover_KE]

Thank you all!_It's really a great place to improve our English._Thank you all again!

I repeat:

Please note, on the way, that we leave a space after a full stop, comma and question mark (and exclamation mark).


​Rover