'Big bug' means ____.

"tooth and nail" means to tried hard or fight with great fury, energy, and all of one's power. 

The correct phrase for the blank is at  large. The full sentence is: "Birds fly at large in the sky."

The correct word for the blank is is. The completed sentence is: "The headmaster along with his colleagues is coming here today." 

Correct word to fill in the blank is changed.. The completed sentence is: "It is high time we changed our food habits."

The correct word to fill in the blank is make/ makes. The complete sentence is: "Two and two make four"

কোনো বাক্যে sub + wish/fancy থাকলে সাধারণত দ্বিতীয় বাক্যে sub + V2 অথবা sub + would/could + v1 বসে।
- তবে, unreal past বুঝাতে to be verb থাকলে তা সর্বদাই were হয়। অর্থাৎ I wish I were child again- আমি যদি আবার শিশু হতাম।