The afternoon classes are more difficult than the morning classes.

No, that is incorrect.

His plan was so unrealistic that no one could believe it.

The specific gravity of this substance is 2.7.

I think waste is an act of economic suicide.

His sarcastic remarks always irritate me.

The labor cost of our project significantly exceeded the budget.

I spread fertilizer in the garden.

That plan is too impractical, it's difficult to implement.

We are growing vegetables without using chemical fertilizers.