Questions

ptr pointer is constant. In ptr = yourbuf the program is trying to modify it, hence an error.

Any person can have only 1 birthday i.e, the day he was born. And every year we celebrate it's anniversaries.

The stability of the ions is determined by the energy of the lone pairs. Carbon has the least effective nuclear charge (Zeff) and so the lone pair on the CH3− ion has the highest energy, making it the least stable ion and so the strongest base. The Zeff increases as we move across the period until we get to fluorine which has the greatest Zeff and so its lone pairs have the lowest energy, making F− the least basic ion.

In order of decreasing basicity they are ranked LiCH3 > LiNH2 > LiOH > LiF. We are dealing with the ions F−, OH−, NH2− and CH3− and so the factor which influences their basicity is the stability of the ion compared to its conjugate acid.

Except pineapple remaining all three are types of apples.

Pineapple is what kind of apple isn't an apple.